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.

The correct answer is: The red ball has greater kinetic energy because kinetic energy is dependent on both mass and speed, and the red ball has a greater mass.