Anyone who knows me well knows that I’m a very competitive person and I love to play ping pong. I have a ping pong table in my basement and my friends and I used to have tournaments and we even had a rule where if one person got a shutout against someone else, the person that lost would have to pay them $5 (this never actually happened because we would never go along with the rule if it did, it was just a joke we had). It also amazes me to watch table tennis on TV during the Olympics because they hit the ball so hard that I never knew how the person returning it doesn’t hit it off the table every time.
Well, it turns out that this has to do with Newton’s first law, an object in motion will remain in motion unless acted on by an external force, and Newton’s third law, for every action there is an equal and opposite reaction. When the person serving hits the ball, the applied force is so great that the returner doesn’t have to add any force to the ball (neglecting air resistance) since the ball hits the paddle with the same force it started with and the action of the ball hitting the paddle causes the ball to change direction. However, air resistance is an external force acting on the ball causing it to slow down, so the player should plan to hit the ball with a small amount of force each time. The force of gravity causes the ball to hit the table on the opposing player’s side, therefore keeping the game in play until one player adds too much force, too little force, or misdirects the ball so that the ball goes off the table or into the net.
Here's a cool video of the best table tennis point ever: