Question

A block of mass $1 \, kg$ is placed on a truck which accelerates with acceleration $5 \, m \, s^{- 2}$ . The coefficient of static friction between the block and truck is $\text{0.6}$ . The frictional force acting on the block is

• A. $5N$
• B. $6N$
• C. $5.82N$
• D. $4.6N$

Answer 1

Answer: (A)

Given, $a=5ms^{- 2},m=1 \, kg,\mu =\text{0.6}$ .
$\therefore $ Maximum static frictional force $f_{s}=\mu _{s}mg=0.6\times 1\times 10=6N$
Force on a block due to acceleration of truck $F_{ext}=ma=1\times 5=5N$
Hence, $F_{ext} < f_{s}$
Therefore, force of friction = external force = $5N$