Question

A boulder of mass 10 kg rolls over a cliff and reaches the beach below with a velocity of 15 m/s. Find:
a. the kinetic energy of the boulder as it lands;
b. the potential energy of the boulder when it was at the top of the cliff
c. the height of the cliff.

pleaseeee

Answer 1

Given:-

• Mass of boulder = 10kg

• Final Velocity = 15m/s

• Acceleration due to gravity = +10m/s

To Find:-

• The kinetic energy of the boulder as it lands

• The potential energy of the boulder when it was at the top of the cliff

• The height of the cliff

Formulae used:-

• Kinetic energy = mv²/2

• Potential energy = mgh

Now,

We will first find the Kinetic enrgy,

→ K. E = ½mv²

→ K. E = ½ × 10 × (15)²

→ K. E = 5 × 225

→ K. E =1125J

But we know that when the body starts moving the Potential enrgy of the body starts Converting into Kinetic enrgy. Before reaching to the last spot it has equal kinetic energy and Potential energy.

Therefore,

→ mgh = 1125J

The Potential enrgy of the boulder when it was on top is 1125J

Now,

→ mgh = 1125J

→ 10 × 10 × h = 1125J

→ 100h = 1125J

→ h = 1125/100

→ h = 11.25m

Hence, The Height of the Cliff is 11.25m