Question

20. Wile E. pushes a 76-kg boulder off of the 90-m cliff in an attempt to hit the Roadrunner. What will the kinetic energy of the boulder be just before it hits the Roadrunner? *NOTE: THIS IS A 2-STEP PROBLEM. INCLUDE THE UNIT IN YOUR ANSWER.

Answer 1

Answer:

67,032 J

Explanation:

According to the law of conservation of energy, the kinetic energy of the boulder just before hitting the Roadrunner (at ground level) will be equal to the gravitational potential energy of the boulder at the top of the cliff, therefore:

$K=U=mgh$

where

m is the mass of the boulder

g is the acceleration of gravity

h is the height of the cliff

Here we have

m = 76 kg

g = 9.8 m/s^2

h = 90 m

Substituting,

$U=(76)(9.8)(90)=67,032 J$