Question

A 20 kg rock is on the edge of a 100 meter cliff. What is the

Answer 1

Explanation:

Given parameters:

Mass of rock = 20kg

Height of cliff = 100m

Unknown:

Potential energy of the rock = ?

Kinetic energy before striking the ground = ?

Solution:

Potential energy is the energy due to the position of a body.

                P.E = mgh

Kinetic energy is the energy due to the motion of a body

                K.E = $\frac{1}{2}$ mv²

m = mass of body

g= acceleration due to gravity

h = height of the body

v = velocity of the rock

At the top of cliff the stone has no kinetic energy because it is as rest. Velocity at rest is zero.

   P.E at the cliff top = mgh = 20 x 100 x 9.8 = 1960J = 19.6kJ

If the rock falls, before it comes to rest, based on the law of conservation of energy, the potential energy of the rock will be the same as the kinetic energy before it falls:

          P.E + 0 = 0 + K.E

Therefore, the potential energy of the rock at rest is the same as the kinetic energy of the rock in flight before it comes to rest.

   P.E = K.E =  1960J = 19.6kJ

Learn more:

Kinetic energy brainly.com/question/6536722

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