# NCERT Class-9 Science Solutions: Chapter 11-Work and Energy Part 2 (For CBSE, ICSE, IAS, NET, NRA 2022)

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**Question 8**:

Water stored in a dam possesses

- No energy
- Electrical energy
- Kinetic energy
- Potential energy

**Answer: D**

**Question 9**:

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

- Only potential energy
- Only kinetic energy
- Half potential and half kinetic energy
- More kinetic and less potential energy

**Answer: C**

**Short Answer Questions**

**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?

**Answer**:

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?

**Answer**:

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.

**Answer**:

He moves on the circular path for one and half cycle . he forgot the correct path at a round about. He moves on the circular path for one and half cycle so the displacement

So total displacement

We have,

Therefore,