Newton's Hidden Fourth Law

Newton never wrote a fourth law, but if he had, it might be this: all three laws work at once, all the time, everywhere.

Consider catching a baseball:

1. The ball in flight stays in motion (First Law)
2. Your glove applies force to slow it — F=ma (Second Law)
3. The ball pushes your hand back as your hand pushes the ball to a stop (Third Law)

This is why you pull your hand back when catching: you stretch out the deceleration time, which reduces the force on your hand. Same momentum change, longer time, less ouch. Boxers roll with punches for the exact same reason.