Work Energy And Power Question 138

Question: A mass m starting from A reaches B of a frictionless track. On reaching B, it pushes the track with a force equal to x times its weight, then the applicable relation is

Options:

A) h=(x+5)2r

B) h=x2r

C) h=r

D) h=(x+12)r

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Answer:

Correct Answer: A

Solution:

[a] KE of Blocks at B=PE at A-PE at B 12mv2=mghmg2r=mg(h2r)

v2=2g(h2r) (i)

Also, mv2r=xmg+mg

Or v2=(x+1)rg (ii) Equating Eqs. (i) and (ii), we get 2g(h2r)=(x+1)gr Or 2gh=(x+1)gr+4gr=(x+5)gr

h=(x+52)r



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