Unit 3P.1:. Size and direction of forces Magnets Springs Science skills: Making and using models Classifying Observing By the end of this unit you should be able to: Recognise that a force acts in a particular direction. Know that there are forces of attraction and repulsion between magnets. Recognise that only certain kinds of materials are magnetic. Recognise that a stretched or compressed spring can exert a force. 65
3.4.1, 3.10.1 Physical processes Size and direction of forces What is a Force? Write as many words as you can linked to the word FORCE, one has been done, don t forget the arrows! Makes things move FORCE It is fun to ride in a wagon. How can we make the wagon move? 66
You can push or pull to make things move. The man holding the handle is pulling the wagon. When you put clothes away, you pull to open a drawer. To close the drawer, you push it. Forces, which can be classified as pushes or pulls, cause objects to start moving, stop moving and change speed and direction. Time to think: Write under the pictures PUSH -AWAY or PULL TOWARDS YOU. ( ) ( ) 67
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Activity1: Materials Aluminum foil, bowl of water, glue, straws, paper, fabric All kinds of different packaging sponge, plastic bottles, Styrofoam. Some ideas to help you! : Process Skills Making and using models Classifying Steps: 1- Use the materials to make a model of a boat. 2- Set the boat on the water. 3- Find ways to make the boat move. 4- Classify the ways. Each time you make the boat move, tell if you are using a push or a pull and the direction. Type of force (push, pull) Direction (right, left, forward, backward) 69
Time to think: Q1- What are 2 ways you can move things? Q2- Write about some thing you moved today at home? Did you push or pull? Activity2: Materials Football Process Skills Observing Steps: 1- Tell one student in each pair to instruct the other to kick the ball with a small push force to the right. Measure the distance the ball rolls. Draw the direction of the movement of the ball. Distance: 70
2-Tell the student again to kick the ball with a big push force to the right. Measure the distance the ball rolls. Draw the direction of the movement of the ball. Distance: What have you observed about the distance the ball rolls? The effects of a force depend on its direction as well as its size. 71
Activity (3): Materials: Blocks, table tennis ball, straw Process Skills: Observing Steps: 1- Build a maze. 2- Put the ball at one end of the maze. 3-Blow the ball with the straw. 4- Observe how the ball moves, stops and changes direction. 5- Move the ball through the maze. Then move it back again. 6- Draw a map of your maze. Draw a line to show where the ball went. 72
Key terms: Force Direction Push Pull Key ideas: Force is a push or pull. It can change the motion of objects. Key Questions Q1- What is force? Q2- What are the 4 things that forces can cause objects to do? 1-2- 3-4- Q3- Write true or false: 1- We can see forces. 2- We can see the effect of forces. 73
3.10.2, 3.10.3, 3.10.4, 3.10.5 Physical processes Magnet Some are round. Some are fancy. One is shaped like a horseshoe. Where have you seen magnets? Circular magnet Bar magnet Ball magnet Horseshoe magnet The picture above shows different kinds of magnets. When a magnet pulls some things toward it, it attracts these things. A magnet can repel another magnet and pushes it away. 74
Magnets have 2 poles. Objects stick to a magnetic pole because that is where the magnetic force is the strongest. South Pole North Pole Activity 4: Materials 2 bar magnets. Steps: Process Skills Observing Investigating 1- Place the North Pole of 2 bar magnets against each other. 2- Draw your observation use arrows to show in which direction they move. 3- Place the South Pole of 2 bar magnets against each other. 75
4- Draw your observation. 5- Place the North Pole of one magnet with the South Pole of the other magnet. 6- Draw your observation. 76
Like poles of a magnet repel or push away from each other. Unlike poles attract or come close to each other. Substances that are attracted to magnets are said to have magnetic properties. Iron, steel, cobalt and nickel are the only common substances that have magnetic properties 77
Activity 5: Materials Magnet, paper, classroom objects; paperclips, eraser, pens, pencils, sharpeners etc.. Process Skills Classifying Steps: 1- Write attracts on one paper. 2- Write does not attract on the other paper. 3- Test things with a magnet. 4- Classify the things. 5- Put them on the correct paper. 6- List the objects in the table. Attracts (Magnetic material) Does not attract (Non-magnetic material) 78
Activity 6: Materials A variety of magnets, paper clips. Process Skills: Comparing Steps: 1-Take a variety of magnets and paper clips. 2-Find out the maximum number of paper clips each magnet will attract hold at the same time. 3- Record your observations. Magnet Bar magnet Horseshoe magnet Circular magnet Number of clips the magnet can hold 4-Write which magnet is the strongest.---------- Different magnets have varying strengths. Ask your teacher to show you this! 79
Activity: Materials Sheets of paper, paper clips, bar magnet. Process Skills Classifying Steps: 1-Take a bar magnet and place a paper on it. Hold it upside down. 2- Drop few paper clips on the paper. 3- Place 1 more sheets of paper. Repeat the same procedures many times. 4- Record your observation. How many paper clips does it hold? Number of sheets 1 sheets 2 sheets 3 sheets 4 sheets 10 sheets Observatio 80
5- Repeat this activity with materials like fabric, aluminum foil, thin wood or even water!. 6- Record your observation. Material fabric Aluminum foil wood water Observation Magnetic force can work through different nonmagnetic materials. Uses of magnets The discovery of magnets was very important because they are used in making many things. Magnets are used in telephones, lights, electric heaters, computers, televisions, door bells and many more. 81
Key terms: Magnet North Pole South Pole Repel Attract Key ideas: There are forces of attraction and repulsion between magnets. Not all metals are attracted to magnets. Key Questions Q1- Which objects will the magnet attract? Object Wooden pencil Steel key Copper wire Cardboard box Iron nail Is attracted Is not attracted 82
Q2- Observe the table and answer the questions. Magnet Horseshoe Bar Round Number of paper clips 6 14 18 A-Which is the strongest magnet? How do you know? B- Which is the weakest magnet? How do you know? Q2-Use the words repel or attract to label the pictures. 83
Springs Springs come in different shapes and sizes. Activity: What do all these items have in common?--------- What happens to a spring if you push it?--------- What happens to a spring if you pull it?---------- After you have pushed or pulled the spring, what does it do?--------------------------------- 84
When a spring is stretched it wants to pull back together - a pull force. When a spring is compressed it wants to push back, a push force. Materials that can return to their original size or shape are called elastic. Activity: Materials Force meter, different weights Process Skills Observing Measuring Steps: 1-Take different force meters. 2- Keep the mass the same. Hang it on the hook. 3- Repeat the same procedure for different weights. 4- Observe and answer the following questions. 85
1.What do you think the spring is doing? 2.What is making it do that? 3.Which way is the spring being pulled? 4.Which spring stretches the most? When the weight is put on the spring it stretches. The stronger spring stretches the least, the weaker spring stretches the most. The stronger spring will be harder to stretch because they have a bigger pull back force. 86
Key terms: Spring Stretch Compress Key ideas: When a spring is stretched it exerts a pull force. When a spring is compressed it exerts push force. Key Questions Q1- Abdullah is pushing on the spring. A-Which way does the spring push on his hand. Draw a arrows? 87
B- Write true or false for each sentence about the spring. 1- It becomes longer when Abdullah pulls it.-- ----- 2- When Abdullah releases it, it returns to the length it was before.------------- C- Which property of the spring has Abdullah explored? Circle your answer. 1- Elasticity 2- Flexibility 3- Softness D- Write the correct scientific term to finish this sentence. Stretching, pulling and squeezing are all ways of applying a -------------- 88