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. $6 \, ms^{- 2}$
• B. $4.9 \, ms^{- 2}$
• C. $3.92 \, ms^{- 2}$
• D. $1 \, ms^{- 2}$

Answer 1

Answer: (D)

Force required to just start the motion is,
$f_{L}=\mu _{s}mg$
Once body starts sliding friction becomes kinetic,

$\therefore $ $a=\frac{f_{L} - f_{k}}{m}=\frac{\mu _{s} m g - \mu _{k} m g}{m}$
$a=\left(\left(\mu \right)_{s} - \left(\mu \right)_{k}\right)g=\left(0.5 - 0.4\right)10ms^{- 2}$
$a=1 \, ms^{- 2}$