Question

A 60 kg 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. $9.8m/s^2$
• B. $3.2m/s^2$
• C. $1m/s^2$
• D. $5m/s^2$

Answer 1

Answer: (C)

$1m/s^2$

The Uniting friction $={\mu }_{s}R$
${\mu }_{s}mg=0.5\times 60\times 10=300N$
Kinetic friction $={\mu }_{k}R={\mu }_{k}mg$
$=0.4\times 60\times 10=240N$
Force applied = 300 N
Net accelerating force
= Applied force - kinetic friction
$\Rightarrow$ ma = 300 - 240 = 60
$\Rightarrow a=\frac{60}{60}=1m/s^2$