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Turning and squashing

Forces and motion · level 1, lesson 5 of 6

A question to start

A football is rolling towards you. You kick it from the side. Does it stop, or go faster, or does something else happen? And what happens to a ball of play dough when you press it?

The idea

A force can do more than start and stop things. It can also:

  • Change the way something is going. Kick a rolling ball from the side, and it turns and goes a new way. A tennis racket sends the ball back the way it came.
  • Change its shape. Press play dough, and it goes flat. Pull a rubber band, and it stretches. Squeeze a sponge, and it gets smaller.
a side kick turns ita press flattens it

Some things spring back when the force goes away, like a sponge or a rubber band. Others stay squashed, like play dough or a crushed can.

On Mars, a rover has to steer round rocks. It turns by pointing its wheels a new way, so the push between the wheels and the ground points along the new path.

Worked examples

1. Bouncing a ball. When a ball hits the floor, the floor pushes it up. It changes the ball's way from down to up, and for a moment it squashes the ball a little.

2. A bow. Pulling the string of a toy bow bends the bow. Let go, and it springs back, pushing the arrow off.

Try it

  1. Name the four things a force can do to something.
  2. What happens to a rolling ball kicked from the side?
  3. Name something that springs back after you squash it, and something that stays squashed.
  4. When a ball bounces, what pushes it back up?
Answers
  1. Start it, stop it, change the way it goes (or its speed), and change its shape.
  2. It turns and goes a new way.
  3. For example a sponge springs back; play dough stays squashed.
  4. The floor.

Common mistake

"Only a big force can turn something." A small push from the side turns a moving thing a little; a bigger push turns it more. Any sideways push turns it some.

Where it leads