There is a rock on the edge of an 85 m high cliff on the moon (no air resistance

Question

There is a rock on the edge of an 85 m high cliff on the moon (no air resistance) with a mass of 52 kg. It has an internal energy of 33 kJ.

Determine the total mechanical energy of the rock (remember you will need the gravitational acceleration of the moon).

Determine the total energy of the rock (E) and the specific total energy of the rock (e).

If the rock falls off the cliff, determine the velocity just before the rock hits the

ground, assuming the final and initial energies must be the same.

Explanation / Answer

1.

1)

The gravitational acceleration = 1.6 on the moon

Total mechanical energy = Potential energy = 85*52*1.6 = 7072 J

2. Tital energy E = 33kJ + 7.072 kJ = 40.072 kJ

specific energy e = E/m = 40.072/52 = 0.771 J/kg

3)

If the rock fall potential energy becomes kinetic..

Kinetic energy = 1/2* m * V^2

V = sqrt(2*7072/52 ) = 16.5 m/s

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