Question

question 3 (1 point)
a ball falls from the top of a building, through the air (air friction is present), to the ground below. how does the kinetic energy (k) just before striking the ground compare to the potential energy (u) at the top of the building?
k is equal to u.
k is greater than u.
k is less than u.
it is impossible to tell.

Explanation:

When a ball falls with air friction, mechanical energy (sum of kinetic and potential energy) is not conserved. Some of the initial potential energy (U) is converted into kinetic energy (K), but some energy is also lost to air friction (as heat, sound, etc.). So the kinetic energy just before hitting the ground will be less than the initial potential energy because energy is dissipated due to friction.

Answer:

C. K is less than U.