The kinetic energy just before hitting the ground is 20,000 J
Explanation:
According to the law of conservation of energy:
"energy cannot be created or destroyed, but only transformed"
In this problem, we have a boulder initially above the ground, and its potential energy is
U = 20,000 J
Its mechanical energy is the sum of its potential energy (U) and kinetic energy (K):
E = U + K
Initially, the boulder is at rest, so the kinetic energy is zero, therefore
[tex]E=U=20,000 J[/tex]
So the total mechanical energy of the boulder is 20,000 J.
The mechanical energy of the boulder is conserved during its fall. Just before hitting the ground, the potential energy has become zero (because the height of the boulder is now zero), so
U = 0
And so,
E = K
Which means that the kinetic energy of the boulder just before hitting the ground is equal to the total mechanical energy: and since the mechanical energy is conserved, we have
K = E = 20,000 J
Learn more about potential energy and kinetic energy:
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