Question

a block of mass m is suspended by a light thread from an elevator . the elevator starts moving up with a uniform acc . the work done during first t sec by tensn in thread ?

although i know how to calculate this ques . i.e w.d =Fds =m(g+a)Xds  where ds=ut+1/2(at2)  because acc is const a/c to ques BUT I want to know for ds why acc is a ,why not (a+g)

Joshi sir comment

tension in the thread depends on g an a both. 

but displacement covered by elevator depends only on the acceleration of the elevator, it does not depend upon the acceleration g thats why we do not use g in that case for finding displacement.

remember that in the problem we have to calculate work done by tension in the thread

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