Question

9. 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. [4]

Answer 1

Answer:

➡️Kinetic energy = ½×mv²

➡️Kinetic energy = ½×10×15²

➡️Kinetic energy= 5 × 225 = 1125 Joule (J)

\small \fbox {The kinetic energy = 1125 J}

The kinetic energy = 1125 J

But when the body starts moving it converts Potential energy into kinetic energy. So , We know before reaching it has equal kinetic energy and potential energy.

Mgh = 1125 J

So, the potential energy of the boulder was on top is 1125 J

Now

➡️mgh = 10× 10 × h =1125 J

➡️mgh = 100h = 1125 J

➡️ h = 1125/100 = 11.25

\small \fbox {So the height of the body is 11.25 m}

So the height of the body is 11.25 m