Q. A block of mass $0.1\ kg$ is held against a wall by applying a horizontal force of $5\ N$ on the block. If the coefficient of friction between the block and the wall is 0.5, the magnitude of the frictional force acting on the block is
A) $2.5\ N$
B) $0.98\ N$
C) $4.9\ N$
D) $0.49\ N$
Explanation
(b) Limiting friction $F_{1} = \mu_{s}R = 0.5 \times (5) = 2.5\ N$
Since downward force is less than limiting friction therefore block is at rest so the static force of friction will work on it
$F_{s} = downward\ force = Weight$
$= 0.1 \times 9.8 = 0.98\ N$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.