All of the following objects are moving at the same speed. Which one has the greatest kinetic energy?

a. a bicycle

b. a motorcycle

c. a car

d. a semi tractor-trailer truck

Having the same speed, a semi tractor - trailer truck has the greatest kinetic energy among the four. This is because kinetic energy is directly proportional with half of the square of the velocity times the mass of the object in motion. As the mass is increased, with the same speed, the kinetic energy increases.