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A block of mass 2 kg is hanging from a l...

A block of mass 2 kg is hanging from a light, smooth pulley through a light string. The kinetic energy of block increased to 16 J in 2 s by applying a constant force F on one end of upper string. Then

A

the force F may be 12 N

B

the force F may be 8 N

C

the potential energy of block may increase

D

the potential energy of the block may decrease.

Text Solution

Verified by Experts

The correct Answer is:
A, B, C, D
If block is moving upward `(2F-mg)=m(dv)/(dt) rArr 2Ft - mgt = mv`
or `2Fxx2 -2 xx 10 xx2 = 2v rArr 2F-20 = v`
Hence, `(1)/(2) mv^(2) =16`
`rArr v=4 m//s therefore` Force applied, `F=12 N`
If block is moving downward, `mgt-2 Ft = mv`
or `(2 xx 10 xx 2) - (2 xx 2F) =8, rArr F=8 N`
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