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tarun_bits

Some very useful points....On Work energy and power

Hi frnz...i hope this is useful...here are some general points which i myself have witnessed and are good concept builders..

1)In the below diagram...work done by the applied force is same wether the force is applied horizontally or it is applied along the plane because the friction is absent if friction has been there than the work would have been different.....

see it yourself in ques>>12 of hcv

2) Work Energy Theorem

The work done by ALL the forces is equal to the change in kinetic energy,,,,wether the forces are conservative, non-conservative or external..

W(c) + W(NC) + W(ext) = K(final) ? K(initial)

3)In some questions like ques 17 of hcv ..if nothing is mentioned about friction..than also u hav to consider it and explore all the cases.

4)one important point I witnessed is that you should use g as 9.8 and not 10 when it is not given.It may cause some good variations otherwise especially in objective questions.

5)the work done is ?FRAME DEPENDENT??

For example>>>you cannot say that the work done by static frictional force is zero?.if you observe it from ground frame for a two block system..it actually does work?.its true that the point of contact does not move relative to any body.

6) Energy is a scalar quantity and so no direction is required ..see ques number 21 in hcv.

7)In the same ques 21 and many other ques u will witness that the mass of the particle is not given??u urself think now what does it signify??

8)In some questions like ques 31 of hcv?u should develop the required constraint relation and than analyse each body separately??

Than see all the forces acting and the work they do..and you can apply the Work ?Energy theorem to it?.

But you should be Very careful in applying Law of conservation of mechanical energy?

9)The Law of conservation of mechanical Energy..

The 2 conditions you sould strictly follow while applying the law of conservation of mechanical energy are as follows>>>

(A) The internal forces should be conservative..If the forces which are non-conservative like Friction are present than you can`t apply it?.

(B) The external forces should be absent or the work done by them sould be zero?

Do rate if you feel a single word useful//

@@@Have a chilling time@@@

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