Question

A small block of mass $m$ is kept on a rough inclined surface of inclination $\theta$ fixed in a elevator. The elevator goes up with a uniform velocity $v$ and the block does not slide on the wedge. The work done by the force of friction on the block in time $t$ will be :

• A. zero
• B. $mgvt \cos^2 \theta$
• C. $mgvt \sin^2 \theta$
• D. $mgvt \sin \, 2 \theta$

Answer 1

Answer: (C)

$mgvt \sin^2 \theta$

Answer 2

$W_{f}=f \sin \theta S$ $=(m g \sin \theta)(\sin \theta)(v t)$ $=m g \sin ^{2} \theta v t$