Question

A block of mass $0.1kg$ is held against a wall by applying a horizontal force on $5N$ on it. If ${\mu }_s$ between the wall and the block is $0.5$ the magnitude of the frictional force acting on the block is :

• A. $0.98N$
• B. $0.49N$
• C. $4.9N$
• D. $2.5N$

Answer 1

Answer: (A)

$0.98N$

$N_r=5kg$

${\mu }_s=.5$

Limiting friction force$=\mu N_r=.5\times 5=2.5N$

$F_{limting}>weight$

So the block is at rest:

$F_s=W=0.1\times 9.8$
$=0.98N$