Class 8 Test Physics CH 4 Energy set 2

1. Define Work. Unit? What is the difference between energy and Work.
2. When does a force perform work?
3. State two conditions when no work is done by a force.
4. The moon is revolving around the earth in a circular path. How much work is done by the moon?
5. A coolie is moving on a road with a luggage on his head. Does he perform work against the force of gravity? Give reasons for your answer.
6. Define the term energy. Unit? How Energy and Work related.
7. What are two kinds of mechanical energy? Their Definition.
8. Give an example to show the conversion of potential energy to kinetic energy when put in use.
9. Can a body possess energy even when it is not in motion? Explain your answer with an example.
10. Name the form of energy stored in a wound up spring of a watch. 

11.  Name the type of energy (kinetic or potential) possessed by the following:

    (a) A moving cricket ball

    (b) A stone at rest on the top of a building

    (c) A compressed spring

    (d) A moving bus

    (e) A bullet fired from a gun

    (f) Water flowing in a river

    (g) A stretched rubber band

12. Give reasons for the following:

    (a) No work is done if a man is pushing against a wall.

    (b) Hammer drives a nail into the wood only when it is lifted up and then struck.

    (c) A horse and a dog are running with the same speed. Which one of them has more kinetic energy than the other.

    (d) A teacher moving around in the class is doing work but a child standing and reading a book is not doing any work.

13. Formula Of Work. What is law conservation of energy.

14. What is Power. Write their Unit with mathematical expression.

15. What is the formula of Potential and kinetic Energy.

16. A car is Displaced through 5 km on application of a force of  700 N. Calculate the work done.

17. A man weighing 70 kg carries a load of 10 kg on the top of a tower 100m height in 3min 20 sec calculate the power.

18. Two body having same mass and are moving with velocity 2v and 3v. what is the ration of their kinetic energy?

19. Siya through a ball with velocity 8m/s from ground. what is the maximum height ball reach. take g=10 m/s^2

20. A mass of 10 kg is dropped from a hight 100cm. find its :

            a) Potential Energy just before dropping.

            b) Velocity just before reaching the ground

            c)kinetic energy at top and just before hit the ground