Question

If mass of $A=10\text{kg}$ , coefficient of static friction= $0.2$, coefficient of kinetic friction = $0.2$. The mass of $B$ is $20\text{kg}$. Find acceleration of masses

• A. $6{\text{m/s}}^2$
• B. $7{\text{m/s}}^2$
• C. $8{\text{m/s}}^2$
• D. $9{\text{m/s}}^2$

Answer 1

The correct option is A $6{\text{m/s}}^2$

FBD of block $A$

$N=10g$
$f_{max}={\mu }_{s}N=0.2\times 10g=2g$

FBD of block $B$

$T=20g$
Here the frcitional force $f_{max}<T$ and so the system will move
$a=\frac{\text{supporting force}-\text{upposing force}}{\text{Total mass}}$
$a=\frac{20g-2g}{30}=\frac{18\times 10}{30}=6m/s^2$