[blacksmythe]

Kinetic energy is a good measure for a baseball, because essentially all of the kinetic energy is being transferred from the small object to you.

Kinetic energy is not a good measure for a car or B-52, as after the collision the large object has essentially the same kinetic energy, and a very small fraction has been transferred to you.

A bicycle is more toward the small object side, as a pedestrian is going to absorb a good fraction of the kinetic energy of the rider, which is much larger than the kinetic energy of the bicycle itself.