Student-friendly bat and ball collision experiment

Sport-related experiments are often crowd-pleasing classics in physics labs. Baseball or softball calculations are often simplified to head-on, energy-conserved collisions between two balls instead of a ball and a bat. But real collisions are not so simple.

To understand a real scenario, Rod Cross developed a student-friendly experiment to determine outgoing ball speed as a function of impact location the bat. Using a baseball bat and ball mounted on separate pendulums, the experiment can be safely conducted in an indoor space. With a video camera and tracking software, the impact location between bat and ball can be determined and used to calculate impact and outgoing speeds.

“Collisions are usually explained to students for idealized, simple cases where two balls collide head-on and where momentum and energy are conserved,” said author Rod Cross. “Real collisions are always different. My experiment shows what actually happens, but it can be understood in terms of the collision between two balls.”

By treating the collision as one between two balls, the math is greatly simplified. The speed of the ball after collision can be easily calculated using just equations for conservation of momentum and the coefficient of restitution, which describes the elasticity of the collision and easily measured in the experiment. This is maximized at a point on the bat where energy loss due to bat vibration is minimal. Students can use this to maximize outgoing ball speed.

The experiment adds a realistic scenario to the library of other baseball experiments. Cross hopes it can be used by teachers to tap into some of their students’ natural interest in baseball or softball to help them learn about real collisions and the physics of the sport.

Source: “A baseball bat and ball collision experiment for students,” by Rod Cross, The Physics Teacher (2025). The article can be accessed at https://doi.org/10.1119/5.0219036 .