Watching the pitcher and how he throws the ball is a big part of hitting. Since different spins on the ball cause it to drop or curve due to friction between the laces and the air, the batter needs to pay close attention. When to Swing Watching the spin determines where and when the batter will swing. He needs to to project the speed of the ball and where it will cross the plate. The angle that which the hits the bat will determine it's angle of projection.
Power When starting to swing, great acceleration takes place and momentum is also being increased.
The power of the batters swing has to do with how much time took place between the start and finish of the swing and how much work was put into the the swing. Newton's third law is important. For every action there is a opposite and equal reaction. This determines how far the ball is hit.