# A spring placed horizontally on a rough horizontal surface is compressed against a block of mass m placed on the surface so as to store maximum energy in the spring. If the coefficient of friction between the block and the surface is μ , the potential energy stored in the spring is

Q: A spring placed horizontally on a rough horizontal surface is compressed against a block of mass m placed on the surface so as to store maximum energy in the spring. If the coefficient of friction between the block and the surface is μ , the potential energy stored in the spring is
(A) μ2m2g2/2k
(B) 2μm2g2/k
(C) μ2m2g/2k
(D) 3μ2mg2/k

Sol: For equilibrium of the block
Fmax – μmg = 0
 F = μmg
 U = F2/2k
U = μ2m2g2/2k

## Author: Rajesh Jha

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