英語時差：動量（上）

You’re cruising down the street on your skateboard. In one hand you have a tennis ball. Halfway down the street is an X painted on the ground. Your job is to drop the tennis ball from your hand so that it hits the X.

When Do You Drop The Ball?

If you try this experiment yourself, you will find that most people will wait until they are right over the X before letting go of the ball.

This, however, is incorrect. If that was your first guess, think again.

Why Won’t It Work?

That’s right–because you are carrying the ball, it already has a forward momentum.