A student riding on a school bus moving northward at 12 m/s throws a softball of mass 0.50 kg straight upward relative to the bus with an initial speed of 8 m/s (also measured relative to the bus). Ignore air resistance.
Answer the following questions about the ball’s translational kinetic energy.
(a) At the instant the ball leaves the student’s hand, calculate its translational kinetic energy relative to (i) the bus reference frame and (ii) the ground reference frame.
(b) The moment the ball reaches its highest point, its speed relative to the bus is zero. Explain whether its translational kinetic energy relative to the ground is also zero at that instant, and justify your reasoning.
(c) Describe qualitatively how the numerical value of the ball’s translational kinetic energy varies with time for an observer on the bus and for an observer on the ground during the complete up-and-down motion.