Question

A $60kg$ body is pushed with just enough force to start it moving across a floor and the same force continues to act afterwards. The coefficient of static friction and sliding friction are $0.5$ and $0.4$ respectively. The acceleration of the body is

• A. $6m/s^2$
• B. $3.92m/s^2$
• C. $1m/s^2$
• D. $4.9m/s^2$

Answer 1

The correct option is C $1m/s^2$

Formula Used: $f=\mu N$
Given: $m=60kg,{\mu }_s=0.5,{\mu }_k=0.4$,
Limiting friction=${\mu }_s=0.5\left(60g\right)=300N$
Kinetic friction=${\mu }_k=0.4\left(60g\right)=240N$
Formula Used: $a=\frac{F_{net}}{m}$
$\because F=300N$
As force is applied just to balance static friction and once block started moving applied force remained the same and kinetic friction started acting on it
Hence, acceleration
$a=\frac{(300-240)}{60}=1m/s^2$