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

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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,