9th work and Energy-Question Solutions

12/16/2014 CBSE



1. Is work done when you are reading book?



Ans: No ,it is because there is no displacement in body.




2. Are you doing work when you are pushing wall or huge rock?



Ans: No work is done as rock does not move. Energy using this time is
converted as heat energy in body.




3. Give an application where a body displaces without application of work?



Ans: Object displaced itself on inclined plane without application of work.




4. �Idenfy two situation where object does not show displacement by the
application of work?



Ans: The two situations are:



(i) if you push a mighty object



(ii) If balanced force act on a body




5. Name an energy cause by sun?



Ans: Hydroelectricity.



6. Name the two source of energy which are not due to sun?



Ans: Nuclear energy and Geo thermal Energy




7. What happen if you are doing work without changing velocity of object?



Ans: You work is stored in the form of potential energy. For example: �When
you compress slinky work done get stored in the form of Elastic potential
energy.




8. Write the expression for power for a body having constants speed?



Ans: �P = Work /velocity




9. How can you say that sun is cause of hydro electricity?



Ans: Solar energy evaporates water and help to form clouds. Cloud get down
on the earth as rain. This water runs in river that is store in dam at high
altitude. When this water allow falling rotate turbine and generating
electricity. Thus that sun is cause of hydro electricity.




10. How is the dropping of ball from height is the an example of
conservation of energy?



Ans: When ball is dropped from high �its gravitational potential energy
decrease and at same time kinetic energy increases as it gain speed



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