We will use the balls to find out about different motions and the forces that make them.
We will do each motion in pairs, across the room.
First motion: a spin.
Spin the ball in front of you. Where did the force, the push or pull, come from to make the ball spin? (Force from your hand to turn it. Unless a student mentions it, skip talking about gravity yet).
Second motion: a roll
Roll towards your partner. Think about what force makes the ball move. The push of your hand.
The third motion may look the same as the roll, but it is different: a slide.
Where does the force come from to make it slide? How is it different from a roll?
Forth motion: Lift.
What force moves it up?
Fifth motion: a fall
What makes it fall? Your hand does not push it. Another force called gravity.
Sixth motion: a bounce.
This time think about the forces on the ball when it hits the floor. What makes it bounce up again? The ground pushing up on the ball when it hits the ground.
Seventh motion: swing
What makes it swing? The pull and push of your arm. Gravity is pulling down on your arm - you can feel it.