Question

A horizontal force F is exerted on a 20 kg block to push it up an inclined plane having an inclination of ${30}^o$. The frictional force retarding the motion is 80N. For the acceleration of the moving block to be zero, the force F must be

• A. 206 N
• B. 602 N
• C. 620 N
• D. 260 N

Answer 1

Answer: (A)

206 N

Balancing forces along the inclined plane, $Fcos\theta =mgsin\theta +f$

$f=80N;\theta ={30}^o$ is frictional force.

So, $Fcos{30}^o=200sin{30}^o+80\Rightarrow F=205.55N$