Question

A block of mass $50kg$ lies on a horizontal surface in a lorry. The coefficient of static friction between the block and the supporting surface is $\mathrm{0.7.}$ If the acceleration of the lorry is $5m/s^2$ , find the frictional force acting on the block $g=9.8m/s$

Answer 1

When body is at rest, static frictional force is,

$F=\mu mg$

$F=0.7\times 50\times 9.8$

$F=343N$

When the body is in motion, the dynamic frictional force is,

$F=ma$

$F=50\times 5=250N$