Question

A horizontal force of $25N$ is necessary to just hold a block stationary against a wall. The coefficient of friction between the block and the wall is $0.4$. The weight of the block is

• A. 2.5 N
• B. 20 N
• C. 10 N
• D. 5 N

Answer 1

Answer: (C)

Given horizontal force $F=25N$ and coefficient of friction between block and wall $(\mu )=0.4$.
We know that at equilibrium horizontal force provides the normal reaction to the block against the wall. Therefore, normal reaction to the block $(R)=F=25N$.
We also know that weight of the block $(W)=$ Frictional force
$=\mu R=0.4\times 25=10N$.