Question

A block rests on a rough inclined plane making an angle of ${30}^0$ with the horizontal. The coefficient of static friction between the block and the plane is 0.8. If the frictional force on the block is 10 $N$, the mass of the block (in kg) is $($take $g=10m{s}^{-2})$:

• A. 2
• B. 4
• C. 1.6
• D. 2.5

Answer 1

Answer: (A)

2

Component of gravitational force along the inclined plane is being opposed by static friction on the block.

Hence, $mg\times \sin \left(\frac{\pi }{6}\right)=Frictionalforce\Rightarrow mg\times \sin \left(\frac{\pi }{6}\right)=10\Rightarrow m=2kg$