A 12.0 kg rock slides off the edge of a bridge and falls into the water 25.0 meters below. what is the kinetic energy of the rock just as it hits the water?

Question

asked Oct 23, 2019 161k views

1 Answer

Chris Harris · Answer 1 · 2019-10-29T21:24:33+0000

During the fall, all the initial potential energy of the rock

U=mgh

has converted into kinetic energy of motion

K= (1)/(2)mv^2

where h is the initial height of the rock, m its mass, and v its velocity just before hitting the water. So, for energy conservation, we have

U=K

and so we can find the value of K, the kinetic energy of the rock just before hitting the ground:

K=U=mgh = (12.0 kg)(9.81 m/s^2)(25.0 m)=2943 J