The Physics of Softball Velocity

A softball's velocity is defined as the speed and direction in which the ball is traveling. Whether you are pitching, hitting or catching a softball, you influence the softball's velocity. During a game, you can use physics to better understand this velocity.

Background

Newton’s Three Laws of Motion explain that an object’s acceleration is determined by the net force acting on the object. Acceleration is defined as an object’s change in velocity. Therefore, you can determine whether an object’s velocity will increase or decrease by examining what forces are acting on it. When you play softball, several forces influence the ball’s velocity, including the force exerted by the bat, gravity, air resistance and friction .

Pitching

Just before you pitch, the softball is at rest in your hand. When you throw the ball, you exert a forward force on the ball toward the batter. As the ball travels toward the batter, air resistance exerts a backward force on the ball. Therefore, two primary forces act on the ball: the forward force exerted by your arm and the backward force exerted by air resistance. However, the force exerted by your arm is significantly greater than air resistance, which means that the net force acting on the ball is in the forward direction. This net force causes the ball to accelerate forward from its rest position, and the ball’s velocity increases toward the batter.

Catching

As a fly ball falls from the sky toward a catcher, two major forces act on it. The force of gravity causes the ball to accelerate downward. However, as the ball falls, air resistance exerts an upward force on the ball. The upward force of air resistance eventually becomes equal to the downward force of gravity, and the net force of the falling ball is zero. This means that the ball stops accelerating downward and falls toward the catcher at a constant velocity, also known as terminal velocity.

Ground Ball

When you hit a softball on the ground, the ball generally rolls rapidly. Once again, two major forces act on the ball. The force exerted by your bat on the ball causes it to roll forward. However, the ground exerts a backward frictional force on the ball that causes it to decelerate. Because friction is the only force continuously acting on the ball as it rolls, the ball decelerates and its velocity decreases. Eventually, the ball comes to a stop and its velocity is zero.