Question

A block of mass $0.1kg$ is held against a wall by applying a horizontal force of $5N$ 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. $2.5N$
• B. $0.98N$
• C. $4.9N$
• D. $0.49N$

Answer 1

The correct option is B $0.98N$

$F=N=5N$

Vertical forces = gravitational and frictional,

$F_g=mg=0.1\times 9.8=0.98N$

$f_{max}=\mu N=0.5\times 5=2.5N$

In vertical direction,

for no relative motion,

$f_{req}=F=0.98N$

$f_{req}<f_{max}$

Hence frictional force on the object $=f_{req}=0.98N$

Option $\text{B}$ is the correct answer.