Disclaimer. 1 Strengthening teaching and learning of forces in Key Stage 3 science Notes for participants

Transcription

1 Disclaimer The Department for Education and Skills wishes to make clear that the Department and its agents accept no responsibility for the actual content of any materials suggested as information sources in this document, whether these are in the form of printed publications or on a website. In these materials icons, logos, software products and websites are used for contextual and practical reasons. Their use should not be interpreted as an endorsement of particular companies or their products. The websites referred to in these materials existed at the time of going to print. Tutors should check all website references carefully to see if they have changed and substitute other references where appropriate. 1 Strengthening teaching and learning of forces in Key Stage 3 science

2 2 Strengthening teaching and learning of forces in Key Stage 3 science

3 Key Stage 3 National Strategy Science Evaluation: Strengthening teaching and learning of forces in Key Stage 3 science For completion by teachers What were the most successful aspects of today s sessions? What changes would you suggest if today s sessions were repeated? Please grade each session on the basis of how well structured and organised it was to meet the learning objectives identified. Session Grade: please ring 1 = Very good, 4 = Poor Comment Pre-unit tasks What do pupils know about forces and the use of force arrows? 2 Visualisation of forces and their effects 3 What do pupils know about forces and motion? 4 Teaching and learning about forces and motion Overall grade for the unit School Post held Please return this form to your tutor before leaving. Strengthening teaching and learning of forces in Key Stage 3 science

4

5 Slide 1.0 Session 1 What do pupils know about forces and the use of force arrows? Slide 1.1 Structure of today Session 1 Session 2 Session 3 Session 4 What do pupils know about forces and the use of force arrows? Visualisation of forces and their effects What do pupils know about forces and motion? Teaching and learning about forces and motion Slide 1.2 Objectives for the unit To consider how diagnostic questions can be used to identify what pupils know and identify areas for development To identify what pupils have been taught in Key Stages 1 and 2 To explore the use of force arrows as a teaching model To explore some of the forces that are difficult to visualise To identify pupils ideas and common misconceptions about forces and motion To illustrate the use of diagnostic questions in the development of pupils understanding of forces and motion To develop a procedure and rules for analysing motion and identifying the forces acting To apply these rules to a range of simple examples of linear motion Handout Strengthening teaching and learning of forces in Key Stage 3 science

6 Slide 1.3 Objectives for session 1 To consider how diagnostic questions can be used to identify what pupils know and identify areas for development To identify what pupils have been taught in Key Stages 1 and 2 To explore the use of force arrows as a teaching model By the end of this session participants should: be familiar with the use of diagnostic questions to identify what pupils already know and areas for development; recognise that topics taught during Key Stages 1 and 2 underpin the key scientific idea of forces at Key Stage 3; be more confident with the use of force arrows and their use as a teaching model. Slide 1.4 Diagnostic question sets Identifying forces The link between force and motion Friction Gravity and freefall Forces in pairs: Newton s Third Law Slide 1.5 Task A Reflecting on the questions that you used with your pupils What did you find out about their knowledge and understanding of forces? the way that they used force arrows? If you managed to use the questions with both Year 6 and Year 7 pupils, how did their responses compare? What, if anything, could you do differently in order to get the most out of your use of these questions with another class? Share your reflections with a neighbour. 4 Strengthening teaching and learning of forces in Key Stage 3 science

7 Slide 1.6 Pushes and pulls! Slide 1.7 How teaching at Key Stages 1 and 2 underpins the key scientific idea of forces at Key Stage 3 4E Friction 5E Earth, Sun and Moon 6E Balanced and unbalanced forces 2E Forces and movement 3E Magnets and springs 1E Pushes and pulls Handout 1.8 Slide 1.9 Forces (contact forces) between objects A force exerted on each object lasts for as long as the objects are in contact. Once they are apart, the forces no longer exist and the interaction has ended. The forces (pushes or pulls) arise during the interaction. A force cannot be put into or stored in an object. 5 Strengthening teaching and learning of forces in Key Stage 3 science

8 Slide 1.10 Task B An example of forces from Key Stage 2 Draw a diagram of a floating object in a beaker of water. Working with a neighbour, share your diagrams giving any additional verbal explanation if necessary. Explain, in particular, how you used force arrows on a sheet of paper. Handout 1.11 Why use force arrows to represent forces? Slide 1.12 Forces cannot be observed directly. Force arrows provide: a useful way of showing the forces acting on objects in a given situation; an indirect way of identifying when and where a force is acting as well as the direction of the force; a way of simplifying/modelling a complex situation so that a prediction can be made about what will happen. Force arrows An acceptable teaching model Slide 1.13 Forces can be measured using non-standard measures, such as the stretch of a spring or elastic band, or standard measures using a forcemeter. The length of a force arrow can be used to give an indication of the size of the force. The direction of a force arrow is more important than the precise point at which it acts. 6 Strengthening teaching and learning of forces in Key Stage 3 science

9 Slide 1.14 Task C Identifying forces in everyday situations In this task, you will see a selection of interactions. Each interaction will be shown in 3 ways: Video clip animation diagrammatic representation. Identify and label the forces acting on the posters provided using the arrow-shaped sticky notes. After each situation, show your labelled diagram and be prepared to justify the force arrows you have used. Handout 1.15 Slide 1.16 Process of identification of forces Identify which forces are acting. Identify where the forces are acting. Identify the size and direction of the forces. Handout 1.17 Objectives for session 1 Slide 1.18 To consider how diagnostic questions can be used to identify what pupils know and identify areas for development To identify what pupils have been taught in Key Stages 1 and 2 To explore the use of force arrows as a teaching model By the end of this session participants should: be familiar with the use of diagnostic questions to identify what pupils already know and areas for development; recognise that topics taught during Key Stages 1 and 2 underpin the key scientific idea of forces at Key Stage 3; be more confident with the use of force arrows and their use as a teaching model. 7 Strengthening teaching and learning of forces in Key Stage 3 science

10 Slide 2.0 Session 2 Visualisation of forces and their effects Slide 2.1 Objective for session 2 To explore some of the forces that are difficult to visualise By the end of this session participants should: have a greater understanding about forces that are difficult to visualise; know some ways to help pupils overcome some of the challenges experienced when learning about these forces; know more about the teaching and learning of specific forces. Slide 2.2 Forces that are difficult to visualise Forces that act at a distance, such as: gravity; magnetism; electrostatic forces. Forces exerted by inanimate objects, such as: the reaction of a surface; friction. Robin Millar, University of York, 2002 Handout 2.3 Handout 2.4 Handout 2.5 Handout Strengthening teaching and learning of forces in Key Stage 3 science

11 A summary of three forces that are difficult to visualise Slide 2.7 Force of gravity: the force exerted by the Earth on an object is a typical everyday example; is really an interaction involving two objects and therefore two forces. Friction: is an opposing force to motion, not a resisting force. Tension: a string, holding an object, exerts an upward force equal to the downward force of gravity on the hanging object. In all of these cases, we are considering one part of an interaction which really involves a pair of forces. Task D Slide 2.8 Working in a pair explore tension and one other force. Tension, and Gravity or friction Report back to the group on how the activity has influenced your ideas about teaching and learning in this aspect of a forces topic. Handout 2.9 Handout 2.10 Handout 2.11 Handout Strengthening teaching and learning of forces in Key Stage 3 science

12 Slide 2.13 Force from a mattress What evidence is there that the mattress is pushing the person upwards? Force from cushion flooring Slide 2.14 Can you see how the flooring is pushing the person upwards? What is different about this example compared to the last one? Why? Force from hardwood flooring Slide 2.15 Can you see how the flooring is pushing the person upwards? Does this mean the floor is no longer pushing the person upwards? Explain your answer. What is different about this example compared to the last one? Why? Task E Slide 2.16 Having considered forces that are difficult to visualise, look at the following diagnostic questions and reflect on the responses you would expect from the pupils you teach: diagnostic questions sets 3 and 4 10 Strengthening teaching and learning of forces in Key Stage 3 science

13 Slide 2.17 Objective for session 2 To explore some of the forces that are difficult to visualise By the end of this session participants should: have a greater understanding about forces that are difficult to visualise; know some ways to help pupils overcome some of the challenges experienced when learning about these forces; know more about the teaching and learning of specific forces. 11 Strengthening teaching and learning of forces in Key Stage 3 science

14 Slide 3.0 Session 3 What do pupils know about forces and motion? Slide 3.1 Objectives for session 3 To identify pupils ideas and common misconceptions about forces and motion To illustrate the use of diagnostic questions in the development of pupils understanding of forces and motion By the end of this session participants should: be aware of the most common pupil misconceptions and misunderstandings that teachers are likely to encounter when teaching forces at Key Stage 3; have identified a number of ways to approach the teaching of forces so that misconceptions and misunderstandings are revealed and challenged. Handout 3.2 Slide 3.3 How teaching at Key Stage 2 underpins the key scientific idea of forces at Key Stage 3 4E Friction 5E Earth, Sun and Moon 6E Balanced and unbalanced forces 2E Forces and movement 3E Magnets and springs 1E Pushes and pulls 12 Strengthening teaching and learning of forces in Key Stage 3 science

15 Slide 3.4 Task F Use the forces cards to construct a mind-map of those aspects that are taught across Key Stage 3. Start by selecting the cards that are most challenging for pupils. Leave plenty of space between cards, so that other statements and useful information can be added. Compare your own mind-map with the version on handout 3.5. Handout 3.5 Handout 3.6 Slide 3.7 Mary Evans Picture Library Handout Strengthening teaching and learning of forces in Key Stage 3 science

16 Slide 3.9 Slide 3.10 Mary Evans Picture Library Mary Evans Picture Library Slide 3.11a Task H Diagnostic questions Individually Answer the questions from the diagnostic question set, Forces and motion 2: the link between forces and motion. Don t take too long over each question your initial ideas are what are needed at this stage. 14 Strengthening teaching and learning of forces in Key Stage 3 science

17 Slide 3.11b In pairs or threes Discuss your answers with a colleague concentrate on the questions where your answers are different. Come to a common view of the correct answer and add any notes to help you explain your reasoning. Consider where the question challenges common misconceptions and how you would need to seek to address these in your teaching. You are going to present your group s reasoning behind one of questions to the whole group. This will include ways in which you might address pupils misconceptions and misunderstandings. Objectives for session 3 Slide 3.12 To identify pupils ideas and common misconceptions about forces and motion To illustrate the use of diagnostic questions in the development of pupils understanding of forces and motion By the end of this session participants should: be aware of the most common pupil misconceptions and misunderstandings that teachers are likely to encounter when teaching forces at Key Stage 3; have identified a number of ways to approach the teaching of forces so that misconceptions and misunderstandings are revealed and challenged. 15 Strengthening teaching and learning of forces in Key Stage 3 science

18 Slide 4.0 Session 4 Teaching and learning about forces and motion Slide 4.1 Objectives for session 4 To develop a procedure and rules for analysing motion and identifying the forces acting To apply these rules to a range of simple examples of linear motion By the end of the session participants should: be more confident in applying the procedure and rules to linear motion in a range of classroom and simple out-ofclassroom situations; have further developed their understanding of Newton s First Law of Motion. The procedure Slide 4.2 Identify all the forces acting on the object you are interested in, noting their directions. Add the forces acting on the object to find the resultant (or total) force acting on it. Apply the following rules: If there is a resultant force acting on an object, this will cause a change in its motion, in the direction of the force. If the resultant force acting on an object is zero, its motion does not change. Handout 4.3 Handout 4.4 Handout Strengthening teaching and learning of forces in Key Stage 3 science

19 Slide 4.5 Applying the rules If an object is moving in a straight line with increasing speed, there is (no / a resultant) force acting on the object, in the direction ( of / opposite to) its motion. If an object is moving in a straight line and is slowing down, there is force acting on the object, in the direction its motion. If an object is stationary, the resultant force acting on it is. If an object is moving at a steady speed in a straight line, the resultant force acting on it is. Handout 4.6 Plenary Objectives for session 4 Slide 4.7 To develop a procedure and rules for analysing motion and identifying the forces acting To apply these rules to a range of simple examples of linear motion By the end of the session participants should: be more confident in applying the procedure and rules to linear motion in a range of classroom and simple out-ofclassroom situations; have further developed their understanding of Newton s First Law of Motion. Handout Strengthening teaching and learning of forces in Key Stage 3 science

20 Slide 4.9 Objectives for the unit To consider how diagnostic questions can be used to identify what pupils know and identify areas for development To identify what pupils have been taught in Key Stages 1 and 2 To explore the use of force arrows as a teaching model To explore some of the forces that are difficult to visualise To identify pupils ideas and common misconceptions about forces and motion To illustrate the use of diagnostic questions in the development of pupils understanding of forces and motion To develop a procedure and rules for analysing motion and identifying the forces acting To apply these rules to a range of simple examples of linear motion 18 Strengthening teaching and learning of forces in Key Stage 3 science

21 Objectives for the unit Handout To consider how diagnostic questions can be used to identify what pupils know and identify areas for development To identify what pupils have been taught in Key Stages 1 and 2 To explore the use of force arrows as a teaching model To explore some of the forces that are difficult to visualise To identify pupils ideas and common misconceptions about forces and motion To illustrate the use of diagnostic questions in the development of pupils understanding of forces and motion To develop a procedure and rules for analysing motion and identifying the forces acting To apply these rules to a range of simple examples of linear motion 19 Strengthening teaching and learning of forces in Key Stage 3 science

22 20 Strengthening teaching and learning of forces in Key Stage 3 science

23 Some key features about forces that pupils need to know in Year 7 Handout 1.8 An important feature in helping pupils to make progress in their knowledge and understanding of forces is to build on what they already know from Key Stages 1 and 2. During Year 7 pupils should apply their knowledge and understanding of forces in everyday situations. The following situations need to be exemplified: the identification of the forces acting when an object speeds up, or slows down, or changes its direction of movement (generally contact forces); the identification of the forces acting when the shape of an object changes (compression forces). Frequent application will help pupils develop a precise knowledge and understanding that forces always arise from an interaction between two objects, and that: during this interaction, both objects experience a force in opposite directions; therefore, forces always arise in pairs one force on each object involved in the interaction. 21 Strengthening teaching and learning of forces in Key Stage 3 science

24 22 Strengthening teaching and learning of forces in Key Stage 3 science

25 Handout 1.11 Examples of Year 6 pupils 1 of 2 work on floating and sinking 23 Strengthening teaching and learning of forces in Key Stage 3 science

26 24 Strengthening teaching and learning of forces in Key Stage 3 science

27 Handout of 2 25 Strengthening teaching and learning of forces in Key Stage 3 science

28 26 Strengthening teaching and learning of forces in Key Stage 3 science

29 Handout Book lying on table 1 of Strengthening teaching and learning of particles in Key Stage 3 science

30 28 Strengthening teaching and learning of forces in Key Stage 3 science

31 Handout Box sitting on floor 2 of Strengthening teaching and learning of forces in Key Stage 3 science

32 30 Strengthening teaching and learning of forces in Key Stage 3 science

33 Handout Apple hanging on tree 3 of Strengthening teaching and learning of forces in Key Stage 3 science

34 32 Strengthening teaching and learning of forces in Key Stage 3 science

35 Handout Ship at sea 4 of Strengthening teaching and learning of forces in Key Stage 3 science

36 34 Strengthening teaching and learning of forces in Key Stage 3 science

37 Handout Space shuttle launch 5 of Strengthening teaching and learning of forces in Key Stage 3 science

38 36 Strengthening teaching and learning of forces in Key Stage 3 science

39 Handout Tomatoes on scales 6 of Strengthening teaching and learning of forces in Key Stage 3 science

40 38 Strengthening teaching and learning of forces in Key Stage 3 science

41 Handout Tug-of-war 7 of Strengthening teaching and learning of forces in Key Stage 3 science

42 40 Strengthening teaching and learning of forces in Key Stage 3 science

43 Handout Dogsled and huskies 8 of Strengthening teaching and learning of forces in Key Stage 3 science

44 42 Strengthening teaching and learning of forces in Key Stage 3 science

45 Handout Boxer with pummel-ball 9 of Strengthening teaching and learning of forces in Key Stage 3 science

46 44 Strengthening teaching and learning of forces in Key Stage 3 science

47 Handout Ice hockey game 10 of Strengthening teaching and learning of forces in Key Stage 3 science

48 46 Strengthening teaching and learning of forces in Key Stage 3 science

49 Handout Astronauts in weightlessness 11 of Strengthening teaching and learning of forces in Key Stage 3 science

50 48 Strengthening teaching and learning of forces in Key Stage 3 science

51 Handout Ten-pin bowling (1) 12 of Strengthening teaching and learning of forces in Key Stage 3 science

52 50 Strengthening teaching and learning of forces in Key Stage 3 science

53 Handout Ten-pin bowling (2) 13 of Strengthening teaching and learning of forces in Key Stage 3 science

54 52 Strengthening teaching and learning of forces in Key Stage 3 science

55 Forces true or false? Handout Read each statement below and write a T or an F in the second column to indicate whether you think the statement is true or false. Statement True or false? 1 The force of gravity is to do with objects falling. Weight is to do with objects feeling heavy. 2 Weight disappears if the air disappears. This is why there is no gravity on the Moon. 3 The weight of an object increases with its height above the ground. 4 Weight and mass are the same quantity. 5 Weight increases if the object is compressed and decreases if the object is spread out. 6 Moving objects try to overcome the force of gravity as they move upwards and cancel it out at the point where they stop. 7 When a ball is thrown upwards, it stops when the upward force on the ball from the hand is equal to the force of gravity. At this point the force on the ball is zero. 8 The force of gravity acts only while objects are moving downwards. 9 Heavy objects fall faster than light ones. 10 To push an object along a flat surface, a force equal to the weight of the object must be applied. 11 When an object is pushed on a flat surface for an instant, the force from the hand is cancelled out by friction and this is why the object stops. 12 Constant motion (i.e. steady speed) requires a force. Based on questions provided by Bradford College Department of Teacher Education. 53 Strengthening teaching and learning of forces in Key Stage 3 science

56 54 Strengthening teaching and learning of forces in Key Stage 3 science

57 Developing pupils visualisation skills in science Handout Strengthening teaching and learning of forces in Key Stage 3 science

58 56 Strengthening teaching and learning of forces in Key Stage 3 science

59 Forces that are difficult to visualise 1 Handout Force due to gravity Gravity is an everyday force experienced by all. Children start to experience and investigate the effect of gravity at an early age. At Key Stage 1 and 2 they will have undertaken activities such as filling plastic containers with feathers and modelling clay. Pupils are asked to predict which container will hit the ground first. The pupils are then asked to close their eyes and state which container hits the floor first. When completed they cannot distinguish which hits the floor first. They also undertake investigations with spinners to distinguish air resistance from gravity, e.g. QCA scheme of work Unit 6E. However, pupils in Years 6 and 7 find the concept of gravity challenging. Like all forces, the force of gravity is an interaction involving two objects. It is one of a pair of forces. The other force is the force exerted by the object on the Earth. As the Earth has such a large mass, this force has no detectable effect on the movement of the Earth. The force on the object is better described as the force exerted by the Earth on the object rather than weight or gravity, as this makes clear both what is causing the force and what it is acting upon. Gravity is a field force similar to magnetic and electrostatic forces. Field forces are not like contact interactions, where the force only lasts for the short time that the objects are touching. Field forces act at a distance and continuously (though they may change in size as the distance between the objects changes). There are some common misconceptions about this force which need to be addressed during Year 7. These include: the idea that gravity depends on the atmosphere, so there is no gravity, for example, on the moon; the idea that gravity gets stronger as you go further from the Earth (based on the observation that objects falling from a greater height land with a bigger bang). 57 Strengthening teaching and learning of forces in Key Stage 3 science

60 58 Strengthening teaching and learning of forces in Key Stage 3 science

61 Forces that are difficult to visualise 2 Handout Force due to tension When a rope is pulled, as in a tug-of-war, there is a force due to tension within the rope brought about by the two pulling forces. The same happens when a string or some other material supports an object. However, the forces here act vertically downwards and upwards. Within the string, where stretching of the fibres occurs, elastic forces act to resist the separation of the particles which make up the fibres. The string exerts an upward force of just the right size to balance the downward force of gravity on the object. Because they act in opposite directions to each other they balance each other out (which is equivalent to saying that they add to zero ). The force due to tension is equal in size to the weight of the object. All materials, for example rope or string, have a specific limit related to the force due to tension. If the force due to gravity exceeds the limiting value of the force due to tension for any given material, it will break and any object suspended by the material will fall. 59 Strengthening teaching and learning of forces in Key Stage 3 science

62 60 Strengthening teaching and learning of forces in Key Stage 3 science

63 Forces that are difficult to visualise 3 Handout Force due to friction Pupils in Year 7 will be familiar with the force due to friction from Key Stage 2. They will have participated in activities, such as using a forcemeter to measure the force needed to drag an object across the floor, or dropping objects of different shapes into a tall cylinder of water. Pupils will know that friction arises when any two surfaces move over one another. They will also know that air resistance and water resistance can also be thought of as forces due to friction, caused by the movement of something through the air or water. However, they will think of friction as resistance to movement rather than a force that acts in the opposite direction to the possible movement of an object. They will have investigated how lubrication affects the movement of one surface over another. At Key Stage 3 pupils will explore in more detail the ways in which a force due to friction can be reduced and situations in which friction is useful. The type of materials and their texture are important contributory factors, as is the speed of movement across surfaces. The roughness of the two surfaces will affect the way that they interact with each other. For example, when sliding a box across a floor, the opposing force provided by a smooth floor will be different to that from a carpet. In this situation the force exerted by the carpet on the box will be greater than that exerted by the smooth floor. For a box that is stationary, the horizontal force exerted by the floor on the box (the friction force) is zero, because there is no sideways force trying to move the box. For a given box and surface, there will be a maximum limit for the friction force. If the limit of frictional force for the box above is 50N, then any pushing or pulling force below or at 50 N will not cause the box to move. However, when a pushing or pulling force rises above 50 N the box will move in the direction of this force. In the diagram below this can be calculated as follows: a pushing force of 60N (to the right) will produce a resultant force (or total force) of 10 N acting on the box (i.e. the sum of 60N to the right and 50N in the opposite direction), and so it will start to move to the right. 61 Strengthening teaching and learning of forces in Key Stage 3 science

64 62 Strengthening teaching and learning of forces in Key Stage 3 science

65 Circus of activities for use in Task D Handout Activities related to tension: 1 Suspend a 100g mass on a piece of string, hung from a retort stand. Suspend another 100g mass on a spring, hung from a second retort stand. What happens when further masses are added to the string and the spring? What forces are involved? What will happen eventually and why? 2 Imagine being responsible for setting up a bungee jump. What forces are involved? How do these forces influence the type of material used for the bungee cord? 3 Consider a tug-of-war competition. How might the competition be different if: the rope was made of a very elastic material such as rubber; the rope was reinforced with steel cords to increase its strength; the rope was made from two sections spliced together at the midpoint the first being of very elastic material and the second reinforced with steel cords? Activities related to the force of gravity: 1 Describe and explain what would happen if you took a football on a journey to the Moon, and tried to keep playing a game of keepy-uppy * throughout all of the following situations: on take off from the Earth; in orbit around the Earth; landing on the Moon. *Keepy-uppy is the game where a player tries to keep a football in the air for as long as possible using their feet, knees, chest or head to kick or hit it. 3 Fill a tall cylinder with dilute wallpaper paste. Drop in objects of different shapes (but as far as is possible the same mass) and observe their motion. The challenge is to produce an explanation of observations made in terms of the forces acting. 2 Drop a coin and a feather down a vertical tube which can be (a) evacuated and (b) filled with air. Predict what will happen and then explain the observations made. 4 Observe the motion of stomp rockets. Explain what forces make the rocket move upwards and why it eventually falls to the ground. Activities related to frictional forces: 1 Push and pull a large box (a tea chest or something similar). Concentrate on feeling the forces acting both before the box starts moving and as it is moving steadily. Provide an explanation for what is experienced. 2 The challenge is to get a trolley (or a model car) from one end of the runway (plank of wood) to the other without touching it. Provide an explanation of what was done and why. Amend the challenge so it is to make the trolley move at constant speed along the runway. What forces are now acting? What would happen if the surface of the runway was changed? For a particular change, explain why. 3 Show a video clip of an ice hockey game. (Use the one from session 1 Task C.) Describe how the motion of the puck differs from the motion of the ball in a game of hockey on grass and explain why. 4 Examine a bicycle (or skateboard). What features make use of forces which help the rider go faster and which slow the rider down (both usefully and not). 63 Strengthening teaching and learning of forces in Key Stage 3 science

66 64 Strengthening teaching and learning of forces in Key Stage 3 science

67 Handout Extended reading stimulus 1 of 3 Extract from Science Web Reader Physics, Nelson Thornes (Publishers) Ltd, Strengthening teaching and learning of forces in Key Stage 3 science

68 66 Strengthening teaching and learning of forces in Key Stage 3 science

69 Handout of 3 Extract from Science Web Reader Physics, Nelson Thornes (Publishers) Ltd, Strengthening teaching and learning of forces in Key Stage 3 science

70 68 Strengthening teaching and learning of forces in Key Stage 3 science

71 Handout of 3 Extract from Science Web Reader Physics, Nelson Thornes (Publishers) Ltd, Strengthening teaching and learning of forces in Key Stage 3 science

72 70 Strengthening teaching and learning of forces in Key Stage 3 science

73 Over the top Handout (Tim Furniss/Genesis Space Photo Library) 71 Strengthening teaching and learning of forces in Key Stage 3 science

74 72 Strengthening teaching and learning of forces in Key Stage 3 science

75 Handout Forces that are difficult to 1 of 2 visualise 4 Reaction (of a floor or other surface) After being taught about a range of forces, including gravity, tension and friction, pupils in Key Stage 3 will begin to understand the reaction (of the floor or other surface) that exists when objects are placed on a surface, or when a force is applied to a surface. A traditional demonstration at Key Stage 3 is to place a textbook on a surface, such as a table, and to then ask pupils to state which forces are acting. Using elicitation questions, the teacher gets pupils to appreciate that although the Earth exerts a force on the textbook (its weight), pulling it downwards, it does not move. Therefore there must be a force acting upwards. This is called the reaction force. Many pupils, and adults, find it hard to understand that an object placed on a table does not fall due to the force of gravity because the table is pushing upwards with an equal force in the opposite direction. A good way to allow pupils to experience the force is to provide them with sponges that they can push and see the force acting back as they remove the depression force. Another good way to demonstrate the force is to obtain a cut out section of mattress that a pupil can stand on. If a spring mattress is not available a block of high density foam could be substituted. The same, or another, pupil can then be asked to stand on a type of cushion flooring. Pupils can then be asked to explain where the force, which is pushing the person upwards, is coming from. 73 Strengthening teaching and learning of forces in Key Stage 3 science

76 74 Strengthening teaching and learning of forces in Key Stage 3 science

77 Handout Finally a pupil can be asked to stand on a hardwood floor whilst others explain where the force that is pushing the person upwards is coming from. Hopefully pupil discussion will lead to the explanation that, although the wooden floor did not visibly distort under the weight of the person, at a microscopic or molecular level it did. There is a limit to the size of the reaction force which the floor can exert on the person or object placed upon it. Once the weight exceeds the maximum reaction force that the floor can produce, the floor breaks! As an additional activity, pupils can be asked to hold a small table and/or laboratory stool up, outstretched in their arms, at 90 to the body. They are then asked to describe what they are doing to hold the small table and/or laboratory stool stationary. This provides the opportunity for pupils to experience the upward force required to hold the object stationary. 75 Strengthening teaching and learning of forces in Key Stage 3 science

78 76 Strengthening teaching and learning of forces in Key Stage 3 science

79 Pupils statements about forces Handout If there is motion there is a force acting If there is no motion, then there is no force acting There cannot be a force without motion When an object is moving, there is a force in the direction of its motion A moving object stops when its force is used up A moving object has force within it which keeps it going Motion is proportional to the force acting A constant speed results from a constant force Force is a property of a single object rather than a feature of interaction between two objects The passive partner in an interaction doesn t exert a force The push back is greater when an object that is pushed doesn t move than it is if the object does move An object which is being pushed where there is little friction does not exert any, or much, push back The sizes of the forces in a pair depend on the masses of the objects, or their motion Friction only occurs between solids Friction depends upon movement Gravity only affects heavy things It is possible to have weight without gravity Heavier objects fall faster Where there is no air there is no gravity Gravity increases with height above the surface of the earth Sources: Making sense of secondary science, Driver et al, Routledge 1994 (ISBN ) EPSE: Diagnosing pupils understanding, University of York Science Education Group Strengthening teaching and learning of forces in Key Stage 3 science

80 78 Strengthening teaching and learning of forces in Key Stage 3 science

81 Handout Strengthening teaching and learning of forces in Key Stage 3 science

82 80 Strengthening teaching and learning of forces in Key Stage 3 science

83 Handout An outline of the ideas about 1 of 2 falling objects developed throughout history Four key figures are important in a potted history of ideas about forces. The part each one played is outlined below. Slide 3.7 The Greek philosopher and scientist Aristotle (~340 B.C.) supported the then popular idea that heavier objects fall faster than light ones, reasoning that this is because bodies fall with speed proportional to their weights. This was, after all, what was, and still is, commonly observed. During the 14th Century a group of Parisian philosophers, including Buridan, devised an alternative set of explanations for motion which included the idea that force is contained within a body. A very common task given to pupils (and adults) requires them to draw the forces acting on a ball which is thrown vertically upwards then falls to the ground. Slide 3.9 Mary Evans Picture Library Mary Evans Picture Library Galileo Galilei ( ) was an Italian scientist and a professor at Pisa and Padua. He realised that Aristotle had not considered carefully the effects of air resistance. In 81 Strengthening teaching and learning of forces in Key Stage 3 science

84 82 Strengthening teaching and learning of forces in Key Stage 3 science

85 Handout one of his many famous thought experiments Galileo reasoned that, for objects falling freely in a vacuum, there were two rules: all falling bodies fall with the same motion; started together they fall together; the motion is one with constant acceleration, that is the body gains speed at a steady rate; it gains the same addition in speed in each successive second. 2 of 2 It is uncertain whether Galileo ever actually performed the famed experiment of simultaneously dropping a heavy and a light object from the leaning tower of Pisa. In various stories the objects are described as a steel and a wooden ball or two iron ones. It is worth recalling, however, that the experiment was more recently carried out on the Moon where the two objects did, indeed, reach the surface together. Slide 3.10 Mary Evans Picture Library Not long after, the development of air pumps allowed Newton ( ) to actually carry out an experiment looking at free fall in a vacuum. He used a guinea (gold coin) and a feather in a long glass tube from which the air had been pumped and showed that they fell together. It isn t recorded whether this was done before or after an apple fell on his head! (For more of that and other aspects of Newton s work see, amongst other sources, The Faber Book of Science.) Later, Newton went on to develop his statements of the Laws of Motion and of Universal Gravitation. As an aside, some historians attach significance to the coincidence of the usual dates given for Galileo s death (1642) and Newton s birth (also 1642). However, Galileo died on January 8th 1642 whereas Newton was born on January 4th in The anomaly in the dates is due to the change in the calendars. The Julian calendar places Newton s birth on Christmas Day 1642 whilst the Gregorian calendar is used for the date of Galileo s death. The reference to Newton s use of a vacuum in his experiment provides a reminder that in so many of the ideas associated with forces we are asking pupils to imagine or visualise a world where there is no friction, either in the form of air resistance or between solid surfaces. Many pupils find this a difficult conceptual leap and teachers need to pay careful attention to the way they help pupils to develop this different way of thinking about an imaginary world. 83 Strengthening teaching and learning of forces in Key Stage 3 science

86 84 Strengthening teaching and learning of forces in Key Stage 3 science

87 Task G Handout A ball is thrown straight up into the air a small distance. After reaching the top of its flight it falls straight down. Path of the ball Draw arrows to show any forces acting on the ball as it moves upwards. Draw arrows to show any forces acting on the ball when it is at the top of its flight. Draw arrows to show any forces acting on the ball as it is moving downwards. 85 Strengthening teaching and learning of forces in Key Stage 3 science

88 86 Strengthening teaching and learning of forces in Key Stage 3 science

89 Forces and motion Handout The basic principle The motion of an object can be explained by considering the forces acting on it The procedure, including two important rules: 1 Identify the object whose motion you are interested in. 2 Identify all the forces acting on this object, noting their directions. 3 Add the forces acting on the object to find the resultant force acting on it. 4 Use the following two rules: if there is a resultant force acting on an object, this will cause a change in its motion, in the direction of the force; if the resultant force acting on an object is zero, its motion does not change. Applying the two rules requires that pupils understand what counts as a change of motion : A change of motion means that the object changes its speed or the direction in which it is moving Therefore, an object at rest (stationary) or one that is moving at a constant speed in a straight line is not changing its motion. In these situations, the resultant force acting on the object is zero. Conversely, an object that is moving in a curved path (e.g. a circle) at a constant speed is experiencing a change in its motion. In this situation, there is a resultant force acting on the object. For objects moving in a straight line, the rules lead to the following conclusions. When there is a resultant force (which is not zero) acting on an object: a stationary object will start to move in the direction of the resultant force, and its speed will steadily increase; an object moving in the direction of the resultant force will continue moving in that direction with its speed steadily increasing; an object moving in the opposite direction to the resultant force will continue moving in that direction with its speed steadily decreasing to zero. If the resultant force continues to act, the object will then start moving in the opposite direction (i.e. in the direction of the resultant force) with its speed steadily increasing. When the resultant force acting on an object is zero: if the object is stationary, it will remain stationary; if the object is moving, it will continue moving at a steady speed in the same direction. 87 Strengthening teaching and learning of forces in Key Stage 3 science

90 88 Strengthening teaching and learning of forces in Key Stage 3 science

91 Understanding constant speed (uniform motion) Handout Almost all pupils in Key Stage 3 will think that an object moving with steady speed requires a net force to keep it moving. Their experience, and that of most adults, is of a world where they have come to terms with friction. In order to move something they have to continue to apply a force so that the object moves in the direction of the force. Newton s First Law of Motion can be described in a number of ways, but generally states that every object moves in uniform motion, in a straight line, unless acted upon by some external force. Such conditions only exist in the type of perfect world (one without friction) that physicists use to help explain the motion of objects. However, in the real world frictional forces act on an object, usually with an opposing force to the one that is trying to move the object. When an object is moving at constant speed the resultant force (or total force) is zero, that is the driving force and opposing forces balance each other out. A stationary object is therefore just a special case of steady motion. In terms of resultant forces, there is no difference between being at rest, and moving uniformly (at a constant speed in a straight line). Objects that have been kicked, hit or thrown A particular situation that pupils find difficult to interpret is the motion of an object that has been set in motion and is now slowing down. Examples include a football that has been kicked and is rolling along the ground, or a ball that has been thrown vertically upwards. In situations like these, many pupils mark a force in the direction of motion. But this force exists only during the interaction that set the object in motion. Once it has left the foot or hand of the person who made it move, there is no force in the direction of motion. The resultant force is in the opposite direction, making the object slow down (and eventually stop, and perhaps start moving in the opposite direction). 89 Strengthening teaching and learning of forces in Key Stage 3 science

92 90 Strengthening teaching and learning of forces in Key Stage 3 science

93 Activity 1 For the activity described below follow the procedure outlined. A parachutist jumps from a plane. She free falls for a few moments then opens her parachute. Some time later she reaches the ground. Procedure Identify all the forces acting on the object you are interested in, noting their directions. Add the forces acting on the object to find the resultant (or total) force acting on it. Apply the following rules: if there is a resultant force acting on an object, this will cause a change in its motion, in the direction of the force; if the resultant force acting on an object is zero, its motion does not change. 1 What are the forces acting? 2 What is the resultant force and in what direction does it act? 3 How does the motion of the object change? 4 What are the main learning points? 5 What are the main teaching points? Handout of 6 Activity 2 For the activity described below follow the procedure outlined. You have a flexible track with a ball bearing. Place the ball bearing near the top at one side of the curve and predict where it will reach on the opposite side after it has been released. Try it and see if you were correct. Change the shape of the track and try again. Procedure Identify all the forces acting on the object you are interested in, noting their directions. Add the forces acting on the object to find the resultant (or total) force acting on it. Apply the following rules: if there is a resultant force acting on an object, this will cause a change in its motion, in the direction of the force; if the resultant force acting on an object is zero, its motion does not change. 1 What are the forces acting? 2 What is the resultant force and in what direction does it act? 3 How does the motion of the object change? 4 What are the main learning points? 5 What are the main teaching points? 91 Strengthening teaching and learning of forces in Key Stage 3 science

94 92 Strengthening teaching and learning of forces in Key Stage 3 science

95 Activity 3 For the activity described below follow the procedure outlined. You have been given an office chair with wheels. Sit on the chair with your feet against a wall. Now push against the wall and experience the resulting motion. Procedure Identify all the forces acting on the object you are interested in, noting their directions. Add the forces acting on the object to find the resultant (or total) force acting on it. Apply the following rules: if there is a resultant force acting on an object, this will cause a change in its motion, in the direction of the force; if the resultant force acting on an object is zero, its motion does not change. 1 What are the forces acting? 2 What is the resultant force and in what direction does it act? 3 How does the motion of the object change? 4 What are the main learning points? 5 What are the main teaching points? Handout of 6 Activity 4 For the activity described below follow the procedure outlined. You have been given a rectangular water bottle and a trough or sink of water. Start with the bottle empty and place it on the water and observe what happens. Then add marbles (or sand) a little at a time and put the bottle back into the water. Procedure Identify all the forces acting on the object you are interested in, noting their directions. Add the forces acting on the object to find the resultant (or total) force acting on it. Apply the following rules: if there is a resultant force acting on an object, this will cause a change in its motion, in the direction of the force; if the resultant force acting on an object is zero, its motion does not change. 1 What are the forces acting? 2 What is the resultant force and in what direction does it act? 3 How does the motion of the object change? 4 What are the main learning points? 5 What are the main teaching points? 93 Strengthening teaching and learning of forces in Key Stage 3 science

96 94 Strengthening teaching and learning of forces in Key Stage 3 science

97 Activity 5 For the activity described below follow the procedure outlined. First find a 1 coin! Now put it on the rectangular piece of card approx 2cm x 2cm, and balance the coin and card on your left thumb with the coin on top. Practise flicking the card away. Procedure Identify all the forces acting on the object you are interested in, noting their directions. Add the forces acting on the object to find the resultant (or total) force acting on it. Apply the following rules: if there is a resultant force acting on an object, this will cause a change in its motion, in the direction of the force; if the resultant force acting on an object is zero, its motion does not change. 1 What are the forces acting? 2 What is the resultant force and in what direction does it act? 3 How does the motion of the object change? 4 What are the main learning points? 5 What are the main teaching points? Handout of 6 Activity 6 For the activity described below follow the procedure outlined. Imagine you are on the London Eye. Describe and explain the forces acting. Procedure Identify all the forces acting on the object you are interested in, noting their directions. Add the forces acting on the object to find the resultant (or total) force acting on it. Apply the following rules: if there is a resultant force acting on an object, this will cause a change in its motion, in the direction of the force; if the resultant force acting on an object is zero, its motion does not change. 1 What are the forces acting? 2 What is the resultant force and in what direction does it act? 3 How does the motion of the object change? 4 What are the main learning points? 5 What are the main teaching points? 95 Strengthening teaching and learning of forces in Key Stage 3 science