# NCERT Class-9 Science Solutions: Chapter 11-Work and Energy Part 2

Question 8:

Water stored in a dam possesses

1. No energy

2. Electrical energy

3. Kinetic energy

4. Potential energy

Question 9:

A body is falling from a height. After it has fallen a height, it will possess

1. Only potential energy

2. Only kinetic energy

3. Half potential and half kinetic energy

4. More kinetic and less potential energy Image Alf Potential and Half Kinetic Energy Image alf potential and half kinetic energy

Question 10:

A rocket is moving up with a velocity. If the velocity of this rocket is suddenly tripled, what will be the ratio of two kinetic energies?

Initial velocity

Initial kinetic energy

Final kinetic energy (K.E.)

Question 11:

Avinash can run with a speed of against the frictional force of, and Kapil can move with a speed of against the frictional force of. Who is more powerful and why?

Given, force applied by Avinash = 10 N

Speed of Avinash = 8 ms-1 ‘

Power of Avinash

Now, force applied by Kapil

Speed of Kapil

The power of Kapil

Since, Avinash has more power W than Kapil. Therefore, Avinash is more powerful.

Question 12:

A boy is moving on a straight road against a frictional force of . After travelling a distance of he forgot the correct path at a roundabout (Figure) of radius . However, he moves on the circular path for one and half cycle and then he moves forward up to . calculate the work done by him.