Question

A yellow ball with a mass of 2 kg is rolling across the floor at 3 m/s. A red ball with a mass of 3 kg is rolling across the same floor at 3 m/s. Which ball has greater kinetic energy, and why?

The yellow ball has greater kinetic energy, because it is rolling at a higher position above the ground.
The red ball has greater kinetic energy, because it has a greater mass.
The yellow ball has greater kinetic energy, because it is rolling at a greater speed.
The red ball has greater kinetic energy, because it is releasing more thermal energy.
A B C or D

Answer 1

B

Kinetic energy KE = 1/2 m v^2.
Yellow: KE = 1/2(2)(3^2) = 9 J.
Red: KE = 1/2(3)(3^2) = 13.5 J.
Both have the same speed, so the more massive red ball has the greater kinetic energy.