Which one has larger kinetic energy: a 500-kg object moving at 40 m/s or a 1000-kg object moving at 20 m/s?

Kinetic  energy is energy possess by an object due to it motion.

Mass 1;  m = 500 Kg   Velocity 1;  V = 40 m/s

Mass 2;  m = 1000 Kg   Velocity 2;  V = 20 m/s

Formula: K.E = 1/2mv²

For Mass 1  K.E = 1/2(500 Kg)(40 m/s)² = 400, 000 J

For Mass 2  K.E = 1/2(1000 Kg)(20 m/s)² = 200,000 J

This solution shows that a larger velocity will have a greater kinetic energy.