Question

A block of mass $1\text{kg}$ lies on a horizontal surface in a truck. The coefficient of static friction between the block and the surface is $0.6$. If the acceleration of the truck is $5{\text{m/s}}^2$, the frictional force acting on the block in Newtons is

Answer 1

Let the acceleration of the truck be towards left.
Pseudo force will act towards the right as shown in the FBD.
Pseudo force = $ma=5N$
From FBD, we get
$f_s={\mu }_{s}R=0.6\times 1\times 10=6\text{N}$
As the force acting on the block is only $5\text{N}$, therefore the static frictional force will also be $5\text{N}$.