Q.
If reaction is R and coefficient of friction is$\ \mu$, what is work done against friction in moving a body by distance d?
A) $\frac{\mu Rd}{4}$
B) $2\mu Rd$
C) $\mu Rd$
D) $\frac{\mu Rd}{2}$
Explanation
(c) [image:6_image105.jpeg]
As shown a block of mass $M\ $is lying over rough horizontal surface. Let$\ \mu$ be the coeeficient of kinetic friction between the two surfaces in contact. The force Of friction between the block and horizontal surface is given by
$\ \ \ \ F = \mu R = \mu Mg$ ($\because R = Mg)$
To move the block without acceleration, the force (P)required will be just equal to the force of friction , ie ,
$\ \ \ \ P = F = \mu R$
If d is the distance moved , then work done is given by
$\ \ \ \ W = P \times d = \mu Rd$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.