Question

The coefficients of static and kinetic friction between a body and the surface are 0.75 and 0.5 respectively. A force is applied to the body to make it just slide with a constant acceleration which is equal to

• A. $\frac{g}{4}$
• B. $\frac{g}{2}$
• C. $\frac{3g}{4}$
• D. $g$

Answer 1

The correct option is A

$\frac{g}{4}$

Force requried to just move the body of mass m, $f_s={\mu }_{s}mg=0.75mg$
Kinetic friction, $f_k={\mu }_{k}mg=0.5mg$
Net accelerating force, $F=f_s-f_k=0.75mg-0.5mg=0.25mg$
$\therefore$ Acceleration, $a=\frac{F}{m}=\frac{0.25mg}{m}=0.25g=\frac{g}{4}$ which is choice (a).