Physics - W.E.P. Question with Solution | TestHub

The work done by a constant force is $W=\vec{F}\cdot \vec{d}$. For the applied force $F$, the component along the displacement is $F\cos \theta$, so $W_F=Fd\cos \theta$. Thus, A is correct. Gravitational force acts vertically downwards, perpendicular to the horizontal displacement, so $W_g=0$. Thus, B is correct. The normal force acts vertically upwards, perpendicular to the horizontal displacement, so $W_N=0$. Thus, C is correct. The normal force is $N=Mg-F\sin \theta$. The friction force is $f_k={\mu }_{k}N={\mu }_k(Mg-F\sin \theta )$. Since friction opposes motion, the work done by friction is $W_{friction}=-f_{k}d=-{\mu }_k(Mg-F\sin \theta )d$. Thus, D is correct.