Movement Needs Energy: Pushes and Pulls
≈ 15 minTo make something move, you have to give it energy — usually by pushing or pulling it. Kicking a soccer ball is a push. Pulling a loaded wheelbarrow is a pull.
A push or a pull can:
- start something moving,
- stop it,
- make it go faster or slower, or
- change its direction.
A goalkeeper's hands push a moving ball to stop it. A player's boot pushes a still ball to start it moving. Same idea, different jobs.
Movement does not last forever. A ball rolling on the ground slowly stops because the rough ground rubs against it. This rubbing is called friction, and it takes the ball's movement energy away.
Worked example. A soccer ball lies still on the field. Nothing happens until a player's boot pushes it — energy in, and now it rolls. Then the keeper's hands push back on it, and it stops. Two pushes: one to start it, one to stop it.
What must you give an object to make it start moving?
A goalkeeper catches a fast ball and it stops. Did the keeper's hands give the ball a push or a pull?
A ball rolling across the grass slowly slows down and stops. What causes this?
You want a rolling ball to change direction. What can do that?