Question

A 5.2 kg rock falls off of a 13 m cliff. If air resistance exerts a force of 16 N, what is the kinetic energy when the rock hits the ground?

Answer 1

Answer:

Kinetic energy, E = 662.27 J

Explanation:

Given that,

Mass of the rock, m = 5.2 kg

It is falls off of a 13 meters cliff.

Force due to air resistance, F = 16 N

To find,

The kinetic energy when the rock hits the ground.

Solution,

Initial velocity of the rock will be zero as it is at rest. Let v is the final speed of the ball. It is given by :

$v=\sqrt{2gh}$

$v=\sqrt{2\times 9.8\times 13}$

v = 15.96 m/s

The kinetic energy of the rock is given by :

$E=\dfrac{1}{2}mv^2$

$E=\dfrac{1}{2}\times 5.2\times (15.96)^2$

E = 662.27 J

So, the kinetic energy when the rock hits the ground is 662.27 J.