Acceleration Of Block Against Friction MCQ - Practice Questions with Answers

• Case 1:- Acceleration of a block on a horizontal surface

• When the body is moving under application of force P, then kinetic friction opposes its motion.

              Let a is the net acceleration of the body.

           From the figure,

               ma = P - F_K

        $a=\frac{P-F_K}{m}$

• Case 2:- Acceleration of a block sliding down over a rough inclined plane

• When the angle of the inclined plane is more than the angle of repose, the body placed on the inclined plane slides down with an acceleration a.

               From the figure,

$\begin{array}{rl}& ma=mg\sin \theta -F\\ & ma=mg\sin \theta -\mu R\\ & ma=mg\sin \theta -\mu mg\cos \theta \\ & a=[\sin \theta -\mu \cos \theta ]\\ & \text{ For }\mu =0\therefore a=g\sin \theta \end{array}$

• Case 3:- Retardation of a block sliding up over a rough inclined plane

• When the angle of the inclined plane is less than the angle of repose, then for the upward motion

$\begin{array}{rl}& ma=mg\sin \theta +F\\ & ma=mg\sin \theta +\mu mg\cos \theta \\ & ma=g[\sin \theta +\mu \cos \theta ]\\ & a=g[\sin \theta +\mu \cos \theta ]\\ & \text{ For }\mu =0\\ & a=g\sin \theta \end{array}$