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Work and Energy CBSE Class 9

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Work and Energy Topics

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Video Based Test funda (Please watch the above videos before attempting this assessment)
Question 1/20

Q 1. While running down the stairs, the work done is

Solution

While running down the stairs, the work done is negative.

Q 2. 1 watt = 

Solution

1 watt = 1 joule / 1 second 

Q 3. Power is expressed as 

Solution

P = Energy consumed / time taken 

Q 4. The work done in moving a body through a distance of 2 m in the direction of force of 30 N is 

Solution

W = F × s

W = 30 N × 2 m

W = 60 J

The work done in moving a body through a distance of 2 m in the direction of force of 30 N is 60 J. 

Q 5. ___________ is a vector quantity. 

Solution

Force is a vector quantity. 

Q 6. When a stone of mass 20 N is revolved continuously with acceleration 3 m/s2 over a circular path by a string of length 10 cm, the work done will be

Solution

When a force is applied on an object moving in a circular path, the displacement is zero and the work done is also zero. 

Q 7. ______ is defined as the rate of doing work. 

Solution

Power is defined as the rate of doing work. 

Q 8. A solar cell converts 

Solution

A solar cell converts light energy to electrical energy. 

Q 9. If a car and a truck move with the same velocity, then the kinetic energy 

Solution

If a car and a truck move with the same velocity, then the kinetic energy of the truck is more than that of the car. 

Q 10. If the velocity of a body is doubled, its kinetic energy becomes

Solution

If the velocity of a body is doubled, its kinetic energy becomes four times the initial value. 

Q 11. An electric iron converts ______ energy to _________ energy 

Solution

An electric iron converts electrical energy to heat energy. 

Q 12. If the mass of a body is doubled, its kinetic energy is 

Solution

If the mass of a body is doubled, its kinetic energy is doubled. 

Q 13. 1 horse power = __________ watt 

Solution

1 horse power = 746 watt 

Q 14. When the ball is thrown up and reaches the maximum height, 

Solution

When the ball is thrown up and reaches the maximum height, potential energy is maximum. 

Q 15. If the velocity of an object is _______, its kinetic energy becomes one-fourth of its initial value. 

Solution

If the velocity of an object is halved, its kinetic energy becomes one-fourth of its initial value. 

Q 16. When a ball reaches the ground after free fall, its final velocity is 

Solution

When a ball reaches the ground after free fall, its final velocity is maximum. 

Q 17. Power required by a body to do work of 50 J in 10 seconds is 

Solution

Power = work / time

P = 50/10 = 5 watt 

Q 18. Kinetic energy is expressed as

Solution

Kinetic energy is expressed as KE =   and KE = F × s. 

Q 19. Which of the following converts chemical energy to electrical energy? 

Solution

A cell or battery converts chemical energy to electrical energy. 

Q 20. When a force of 50 N is applied on an object weighing 100 N, the work done is

Solution

When a force of 50 N is applied on an object weighing 100 N, the work done is zero, as the object will not get displaced. 

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Work and Energy Notes

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