GoalRemember how forces change movement and shape, and how we choose, test and change materials.
New words
force · a push or a pullnatural · comes from plants, animals or the groundproperty · what a material is like, such as hard or waterprooffair test · a test where we change only one thing
Explanation
A force is a push or a pull. A force can start something moving or stop it. It can make it go faster, slower or a new way. A force can also squash, stretch, bend or twist things. A bigger force makes a bigger change. Some materials are natural, such as wood, wool and stone. Others are made by people, such as glass and plastic. We choose a material because of its properties, and we test materials fairly. Heating and cooling can change materials. Some changes can go back, and some cannot.
Worked examples
Malika gives her skateboard a small push, and it rolls slowly. Then she gives it a big push, and it zooms away.
Kamol presses his thumb into a lump of clay. The push makes a dent, and the dent stays. When he presses a sponge, it springs back.
A frying pan is made of metal, so it can get hot without melting. A pan made of chocolate or ice would melt at once. The right material does the job.
Class activity
Bounce test (with an adult): find three balls, such as a rubber ball, a tennis ball and a ball of scrunched-up paper. Predict which will bounce highest. Drop each one from the same height onto the same floor, next to a wall. Your adult marks how high it bounces. Change only the ball. Write your results in a table and say which ball bounced highest.
Practice
1
Gulnora pulls her suitcase on wheels to the car. Then she pushes it into the boot. Name the two forces.
First a pull, then a push.
2
Which two of these are made by people?
A, the bottle, and C, the brick.
3
In the bounce test, write two things that must stay the same.
For example: the height the ball is dropped from, the floor, and the way it is dropped.
4
Can each change go back? A chocolate bar melts in the sun. A cake mix is baked in the oven.
The chocolate can: it goes hard again when it cools. The baked cake cannot turn back into runny cake mix.
