Discussion Forum



1)

A small block of mass of 0.1 kg lies on a fixed inclined plane PQ which makes an angle $\theta$ with the horizontal. A horizontal force of 1 N acts on the block through its centre of mass as shown in the figure. The block remains  stationary if (take g=10m/s2)

24112021631_m4.PNG


A) $\theta=45^{0}$

B) $\theta$ > $45^{0}$ and a frictional force acts on the block towards P

C) $\theta$> $ 45^{0}$ and a frictional force acts on the block towards Q

D) $\theta$ < $45^{0}$

Answer:

Option A,C

Explanation:

W=mg=0.1 x10=1N

9112021299_k4.PNG

 $F_{1}= $ component of weight

 =1$.\sin \theta= \sin \theta$

 $F_{2}=$ component of applied force

 =$1. \cos \theta= \cos \theta$

 now,  at $\theta= 45^{0}$ :$F_{1}=F_{2}$  and biock remains stationary without the help of friction.

 For  $\theta > 45^{0}$ ; $F_{2}>F_{1}$,  so friction will act

towards Q.

 For $\theta <45^{0}$ , $F_{2} >F_{1}$ ,

and friction will act towards P.