Question

A horizontal force just sufficient to move a body of mass $4kg$ lying on a rough horizontal surface, is applied on it . Coefficients of static and kinetic friction are $0.8$ and $0.6$ respectively. If the force continues to act even after the body has started moving, the acceleration of the body is:
$(g=10m{s}^{-2})$

• A. $6m{s}^{-2}$
• B. $8m{s}^{-2}$
• C. $2m{s}^{-2}$
• D. $4m{s}^{-2}$

Answer 1

Answer: (C)

$2m{s}^{-2}$

Force responsible for increase in velocity $=({\mu }_s-{\mu }_k)mg$

$=(0.8-0.6)\times 4\times 10$

$=0.2\times 4\times 10=8N$

Therefore, $a=\frac{8}{4}=2m{s}^{-2}$