Unit 2P 1: Pushes and Pulls Changing shape Speeding up and slowing down Science skills: Classifying Predicting Measuring By the end of this unit you should be able to: Identify the effects of forces, such as squashing, twisting and stretching. Know how pushes and pulls are used to make familiar objects speed up and slow down. 65
2.8.1 Physical processes Pushes and Pulls Have you ever wondered what makes these things move? Look at these toys, how do they move? Can you describe what you have to do, in order to make them move? ------------------------------------------ I am sure you used the word pull or push pull and pushing are what we call FORCES. The more FORCE you use ( stronger the push or pull!) the more the object moves. 66
You can use a force to move objects up, down, right or left. You can make it move in straight line, a curve or even a zigzag. Think and discuss How do you use forces to move things every day? --------------------------------- You can move things with a push or a pull. Force: Is the push or pull that make something move. When you push something really hard, you are using a big force. If you push something softly, you use a small force. 67
Activity (1): Draw something that you can move by pushing or pulling and say if you need a small force or a large force 68
Push and pull are forces. Push: moving things away from you Pull: moving things towards you Activity (2): What force do you use to put these clothes on? Complete this table. For example: when you put socks on do they use a push or a pull force? Clothes Push Pull Socks T-shirt Jumper Scarf 69
2.1.5, 2.8.2 Physical processes Changing shape When you push or pull something you force it to move or to change shape. can change an object s shape Which of these objects you can change the shape of by pushing? Put a circle to show your answer. Rubber band Cushions Sponge Which of these objects you can change the shape of by pulling? Put a circle to show your answer. Cotton Blue-tack Bamboo cane 70
You can change the shape of a lot of materials by pulling or pushing. Also you can stretch, squash, twist objects to change their shapes. Some materials or objects go back to their old shape after stretching, squashing and twisting. Twisting Bending Stretching Squashing 71
Activity (1) Materials: sponge, modeling clay, dough, bag of sand, balloon Process Skills: Predicting, Can you change the shape of these objects -? What type of forces you will use to change shapes of these objects? Predict. Now Test, then Record your results, but putting the name of the materials in the right column, remember it can be in more than one column! Objects or Materials can be changed by squashing twisting stretching 72
Activity (2) Draw a picture of yourself when you are doing an activity where you change the shape of something. Things like: Jumping up and down on a trampoline. Jumping up and down on a bouncy castle. Walking on wet sand. Squeezing a balloon. 73
2.8.3,2.1.3 Physical processes Speeding Up or Slowing Down? can change the way things move. can Start and Stop things moving. can make things go Faster or Slower Think and Discuss If you are at play ground riding a bicycle. Think about what forces you use to make yourselves start moving, get faster (speeding up), slowing down and finally stopping. Stages on our bike! What forces do you use, (describe it) Push? Pull? Etc.. Starting Going faster Slowing down Stopping 74
Activity (1): A snail and a rabbit have races against each other, but the snail always loses. The sheep offers to help. Does the sheep have to push or pull the snail to make him speed up? ------------------------------------- After the race the sheep goes too fast down the hill. Does the snail have to pull or push the sheep to stop him? ---------------------------------- 75
Activity (2) Materials: toy cars, ruler or meter stick Process Skills: predicting. Measuring Look at these toy cars. Think Which of the cars would travel the furthest and why? Work in pairs. Do the prediction first! Push the toy car softly and measure the distance it travels. Your partner should mark where it stops using his/her finger. Measure using a ruler. Push the same toy car again,but this time with a stronger push. Measure the distance again. Complete the table - My prediction Distance travelled. Soft Push Hard Push I conclude harder the push the.. the car moves... 76
A project: make an exhibit Label one side of your exhibit push and the other side pull. Look for objects that you move by pushing or pulling. Put the objects in the right area in your exhibit. You can add further items by drawing them! Explain how you push or pull to make them move. Key words: Force, squash, twist, stretch, push, pull, pushing, pulling, twisting, stretching Speed up, slow down, start, and stop Key Idea: Push and Pull are types of forces. can change the shape of things. can make things speed up, slow down, stop. 77
Key Questions 1. Name two objects that you can change the shape of by squeezing. 2. Name two objects that you can change the shape of by stretching. Look at the table and answer these questions. Car Red car Blue car Green car Black car How far it went 6 bricks 10 bricks 2 bricks 1 brick 1.Which car travelled the furthest? 2.Which car travelled the length of 1 brick? 3.Which car travelled the length of 6 bricks? 4.Put the cars in order; start with the car that went furthers. 78