Physics and Softball

I went home over the past weekend and on Saturday I went to watch my old softball team play in a tournament. As I was watching the games, I realized how physics plays a large role in the pitching and hitting of a softball.

For starters, the kinetic energy (velocity) of the softball is equal to the net work done by the pitcher, which is equal to the product of the displacement of the ball and the forces parallel to the displacement. The pitcher does a windmill before releasing the ball because this increases the displacement of the softball, increasing the velocity of the ball when it is released. The increase in displacement of the ball allows for a greater initial velocity upon release than if the ball was just pulled back and thrown in the forward direction, like in a normal throw. The pitcher also takes several other steps to ensure that the ball reaches peak potential initial velocity. Rocking slightly before releasing the ball causes a forward shift in weight that increases the momentum of the beginning of her windmill. The momentum of the pitcher’s fastball could be calculated by multiplying the mass of the softball by the average velocity of her fastball. 

p=(0.1984 kg)(26.82 m/s)= 5.32 kgm/s. This differs significantly from the momentum of the pitcher’s changeup, p=(.1984 kg)(18.78 m/s)= 3.72 kgm/s. This large change in momentum is part of the reason why it is so hard for a batter to hit a changeup when they are expecting a fastball. They are expecting the ball to be coming in with a much larger momentum so they are often swinging before the ball has reached them.

The initial velocity of the softball when it is released will not be the velocity of the ball when it reaches the batter, as gravity and air resistance need to be taken into account. The change in kinetic energy of the ball as it travels from the pitcher’s hand to the catcher’s glove can be found by: ½(m_ball)(V_{Final of the ball} – V_{initial of the ball}). The V_{Final of the ball} is equal to 0 m/s and the V_{initial of the ball} is the speed of the ball when it leaves the pitcher’s hand.

The laces of a softball also have a purpose related to physics. The laces create small turbulences in the air so that air remains near the ball for a longer period of time than if the ball were completely smooth. These small turbulences reduce drag on the ball as it travels through the air (a similar thing occurs with the placoid scales of sharks which we learned about in vertebrate zoology).

Hitting in softball also depends largely on physics. Newton’s first law states that an object in motion stays in motion unless acted upon by an outside force. The softball will continue in the path of motion from release of the pitcher’s hand to the catcher’s glove unless the batter is able to hit the ball. The batter also wants to hit the ball on the sweet spot of the bat to achieve the best hit. The sweet spot of the bat is the point of the bat that causes minimal vibration from contact with the ball, which maximizes the energy transfer from the batter’s swing to the ball, therefore maximizing the distance traveled by the ball. A batter is able to tell when they hit the ball with the sweet spot of the bat because they do not feel the vibration or sting in their hands.