4.2 Forces: identifying, measuring and representing motion, turning effects, pressure

Transcription

1 1 of 7 The National Strategies Secondary 4.2 Forces: identifying, measuring and representing motion, turning effects, 7 recognise the forces acting on an object in different situations distinguish between situations involving balanced and unbalanced forces recognise that forces can combine or wholly or partly cancel each other out and their size and direction can be represented using arrows recognise that there are contact forces and forces that act at a distance recognise simple situations where forces are balanced or unbalanced. use the model of arrows to describe the direction and size of forces. recognise that weight is the force of gravity on an object. distinguish between contact forces, e.g. pushes, pulls and friction, and remote forces, e.g. gravity, magnetic attraction and repulsion. describe simply the changes in movement or shape of an object in terms of the forces acting on it. recognise that gravity is a force that has size and direction and acts on all objects. recognise where forces are balanced or unbalanced and use the arrow model to show direction of motion. use ideas of the turning effect of forces to predict whether objects will turn and their direction of rotation. explore the relationship between force, area and. Create opportunities for pupils to use the model of force arrows to explain the effects of balanced and unbalanced forces on objects. Challenge pupils to explore and explain the effect that gravity has on a mass and hence the difference between mass and weight. Provide pupils with first-hand opportunities to explore the nature of magnetic fields and to think creatively to develop their own explanations of these effects. Provide pupils with opportunities to explore how well the model of balanced forces explains the effect of opposing turning forces. Provide opportunities for pupils to explore and explain patterns in data related to the effect of spreading a force out over a greater area. Support pupils in exploring possible misconceptions they might have about forces, e.g. objects run out of force or force is the same as energy. Are forces really balanced? Is friction a drag? Are dieters really losing weight? Are contact forces stronger? What happened before Newton invented gravity? If the upthrust from the water keeps an ocean liner afloat, why doesn t it push people right out of the water? What would be the benefits and issues in a perfectly smooth world?

2 2 of 7 The National Strategies Secondary 8 apply ideas about balanced and unbalanced forces to explain the way objects move investigate situations where forces are applied over large and small areas or have a turning effect recognise that forces at a distance get weaker as the distance increases recognise the differences between the everyday and scientific way of talking about. identify situations in which opposing forces partly or entirely cancel each other out. explain how the quantification of the arrow model improves the description of the direction and size of forces. explain the difference between mass and weight. describe the shape and direction of a magnetic field around a bar magnet using an arrow model. explain the behaviour of moving and stationary objects in terms of two or more forces acting on them describe qualitatively how weight would differ in other parts of the solar system use qualitative models to describe motion in terms of speed, distance and time describe changes in movement using an arrow model to indicate the size of the applied force and where it is applied in relation to the pivot use the relationship between Challenge pupils to develop the model of balanced and unbalanced forces to explain the effects of combinations of forces on objects, including situations in which the forces may not be apparent, such as a reaction from the ground or upthrust from water. Provide pupils with the opportunity to use and compare the models of magnetic fields and current flow to construct explanations about the similarities and differences between the magnetic fields of permanent magnets and electromagnets. Structure opportunities to use the models of forces and particles to explain the relationship between air resistance and friction and explore any misconceptions. Challenge pupils to use the model of force arrows to construct and evaluate explanations of the phenomenon of weightlessness. Create opportunities for pupils to evaluate whether the selection and management of variables in an investigation about the effects of have affected the pattern of results. Involve pupils in exploring the models used to explain quantitatively the effects of a force applied over an area or of more than one turning force being applied to an If forces cancel each other out, do they still exist? Are all magnetic fields the same shape? What is a gravitational field? Can water provide a bigger reaction force? Why do elephants have big feet? Is a drawing pin well designed? What are the bends? Is gravity the glue of the solar system?

3 3 of 7 The National Strategies Secondary 9 recognise how simple quantitative relationships can be applied to the way objects move (including balanced and unbalanced forces) recognise how simple quantitative relationships can be applied to situations where forces are applied over large and small areas or have a turning effect, force and area as a qualitative model to explain familiar observations, e.g. the use of caterpillar tracks or snow shoes explain familiar observations, e.g. drinking through a straw, in terms of the effects of unequal identify situations where forces on an object are less obvious, e.g. upthrust of water on a boat. apply the model of quantified arrows to predict the movement of an object. explore the misconceptions relating to weightlessness. investigate the link between magnetism and electricity, and compare the magnetic field of a wire carrying current with that of a bar magnet. use ideas of balanced and unbalanced forces to predict the motion of objects, e.g. up thrust of water on a boat explain, using data, how the force of gravity between two bodies is dependent on mass and distance apply and use models to explain how, if the forces on an object are balanced, it is not object. Create opportunities for pupils to gather evidence from primary and secondary sources and use the force arrow model to analyse the effects of balanced and unbalanced forces. how well the particle model can be used to explain the effect of air resistance. Challenge pupils to use the model of speed = distance/time to describe and predict motion and then to identify any weaknesses in it. Provide opportunities for pupils to challenge each other s predictions about the direction of motion of an object from the size and direction of the forces acting on it. Provide pupils with the opportunity to use the model of moments and evidence from primary and secondary sources to explain the relative stability of a range of objects. Provide pupils with the opportunity to develop the model of to explain the effect of at various depths in a liquid. Create opportunities for pupils to examine What happens when an irresistible force meets an immovable object? Does speed kill? Is a double-decker bus safe? Why wear a space suit? Do forces always direct movement? Can levers move anything? Is it ever possible to completely escape from the Earth s gravitational field?

4 4 of 7 The National Strategies Secondary 10 use simple quantitative relationships to make predictions in more complex situations use simple relationships involving more complex quantities to make quantitative predictions in familiar situations accelerating use quantitative models to calculate the turning effect of a force in simple situations apply quantitative models to explain in terms of force and area apply models of and of particles to explain atmospheric identify and label forces in more complex situations, e.g. forces in elastic collisions evaluate the strengths and weaknesses of using the arrow model to represent forces link ideas and evidence relating to gravity investigate the interrelationship between the two magnetic fields in a simple electric motor explore the force on an object in circular motion and adapt models to explain it determine acceleration due to gravity and apply this in a range of situations use and apply graphical models to describe motion in terms of velocity and acceleration the strengths and weaknesses of models related to the representation of aspects of forces and decide if they are good enough models. Create opportunities for pupils to research examples of factors that have impacted on the development of the models used to explain forces, e.g. predicting the motion of the planets. Plan opportunities for pupils to develop the model of balanced and unbalanced forces to describe and predict the motion of accelerating objects. the use of graphs as a model to describe and explain the motion of objects. Challenge pupils to use the model of acceleration = force/mass to describe the motion of objects and then to identify any weaknesses in it. Provide pupils with the opportunity to explore primary and secondary evidence and use the models of force arrows to construct explanations of circular motion. Challenge pupils to explore how well the models of particles and can be used to explain the effects of. Is perpetual motion an impossible dream? Do people make cars unstable? Is it true to say we are living at the bottom of an ocean of air? Can you brew up on a mountain? Does more energy mean more? Is there a speed limit for particles? Was the bicycle dynamo a good idea? If you connected a motor to a generator would they just keep each other turning?

5 5 of 7 The National Strategies Secondary 11 use relationships involving more complex quantities to make quantitative predictions in more complex and unfamiliar situations use the relationship of turning moment = force distance as a model to predict the distance unequal masses would need to be placed from the pivot to balance a seesaw apply a quantitative relationship to calculate s using familiar and unfamiliar examples explain the behaviour of gases in terms of the kinetic theory develop general rules to describe how forces affect objects in complex situations, e.g. collisions between vehicles explore scale drawings as a model to show vectors explore misconceptions relating to gravity, e.g. gravity is caused by Earth s spin or magnetism or atmosphere explore the general relationship between currentcarrying conductors and magnetic fields in electromagnetic (EM) induction explain the relationship between forces in familiar and unfamiliar contexts using quantitative models, e.g. impulse, force, time and acceleration of an object on a Challenge pupils to use the models of forces and particles to describe and explain the behaviour of objects falling through fluids, including the phenomenon of terminal velocity. Provide structured opportunities for pupils to use the model of energy transfer to explain the development of road safety provision, e.g. seat belts, speed limits and air bags. the model of momentum, and use this to explain the relationship between speed and mass in collisions and the effects experienced during road-traffic accidents. Provide pupils with the opportunity to explore how well the models of force arrows and circular motion can explain the causes and effects of changes to circular motion. changes in circular motion and explain If there is an equal and opposite reaction to every force, does this mean that all forces are balanced? Can you hear gas if the temperature is high enough? Will the generator save the landscape or destroy it? Does gravity affect height? Do lifts defy the laws of physics?

6 6 of 7 The National Strategies Secondary Extension understanding of forces in explanations of observations and phenomena to complex and unfamiliar contexts use valid and rational argument to offer solutions to problems arising from the applications and implications of forces circular path link the ideas of motion and gravity to explain why celestial bodies orbit each other use the relationship between mass, force and acceleration to describe the motion of an object apply the relationship turning moment = force distance to problems in unfamiliar contexts, e.g. to explain the stability of differently shaped objects apply quantitative relationships to explain how liquids behave under use knowledge and understanding of the gas laws to explain what happens to the air inside a tyre during pumping apply general rules to describe how forces affect objects in complex and less familiar situations, e.g. collisions between particles apply the scale drawing approach to more complex situations, e.g. to explain the forces acting on satellites in orbits of different heights explain ways in which the principles of electromagnetic (EM) induction can be used to these changes using a combination of force arrows, circular motion and acceleration models. how the inter-relationship between the three dependent variables of, volume and temperature can be investigated Provide pupils with opportunities to research various sources of evidence and use the models of particles and to construct explanations of at the microscopic level.

7 7 of 7 The National Strategies Secondary improve the effectiveness of an electric motor understanding of gravity to explain non-circular orbits, such as those of comets understanding of forces to explain momentum in collisions and explosions apply the principles of moments and stability to more complex situations, e.g. altering the design of a double-decker bus so that it passes the tilt test apply quantitative relationships to the solving of problems involving the transfer and multiplication of a force by means of hydraulics understanding of to explain a range of phenomena, e.g. cooking at high altitude, sterilisation using cookers