A tennis ball of mass 58 g repeatedly bounces on a laboratory floor
PHYSICS · Multi-part · AP · Physics 1: Algebra-based · Work Energy and Power · Work Energy and Power
Problem
A tennis ball of mass 58 g repeatedly bounces on a laboratory floor. Two students analyze the motion but choose different reference points for gravitational potential energy.
• Student A defines Ug=0 at the floor.
• Student B defines Ug=0 at the point 1.00 m above the floor.
Assume air resistance is negligible and the ball is treated as a point mass.
(a) Describe how the numerical values of the ball’s gravitational potential energy at the moment it leaves the racket 2.40 m above the floor differ for the two students. Express each value symbolically in terms of m, g, and given heights, and explain the sign (positive, negative, or zero) for each observer.
(b) Immediately after the ball rebounds from its first impact, it reaches a maximum height of 1.60 m above the floor. Calculate the change in the ball’s gravitational potential energy for this rebound as determined by each student. Show algebraic steps and include units in your final numerical answers.
(c) Explain why both students must obtain the same value for the ball’s kinetic energy at the top of the rebound, even though their individual potential-energy values are different.
(d) Student A claims that mechanical energy is conserved during the bounce because gravitational and kinetic energies exchange while total energy remains constant. Critically evaluate this claim, citing physical evidence from the scenario to support or refute the statement.