How to Hit a Home Run
One could guess that hitting a home run depends on the pitch and the force of the bat on the ball. However, not many people realize the importance of "follow through." When a pitcher throws a ball toward the home plate, it has a certain momentum due to its mass and velocity. Most pitches thrown in the major leagues are around 100 mph or 160 km/hr. In order to hit a home run, the batter must cause a significant change in momentum because because the batter wants the velocity of the ball to be in the opposite direction and at the greatest speed possible.
Now consider the momentum change of the ball in terms of impulse. Impulse is equal to the change is momentum which is the sum of the forces multiplied by time. To get the greatest impulse, meaning the greatest change in momentum, you want your force and time to be as big at possible. The batter can only apply so much force, so in order to get the greatest impulse, the batter should increase the time of impact between the baseball and bat, known as "follow through". This can also be applied to tennis or golf.