- Friend or Volunteer
- Ask your friend or volunteer to sit or stand on the skateboard, while holding the ball.
- Push the skateboard forward.
- While rolling the board, let the volunteer toss the ball in the air.
- Observe the ball trajectory.
From your observation, you would have seen that the ball would have moved sideways and landed in your hands despite the person moving forward. The ball would be retaining its original horizontally motion in a manner as if neither the volunteer nor the ball has moved sideways primarily.