A block of mass 48   kg kept on a smooth horizontal surface is pulled by a rope of length 4   m by…

Given,
Mass of block $\left(M\right)=48 \mathrm{kg}$

Linear density of string $\left(\lambda \right)=0.5 \mathrm{kg} {\mathrm{m}}^{-1}$

Length of string $\left(l\right)=4 \mathrm{m}$

Force applied $\left(F\right)=25 \mathrm{N}$

Total mass of the system $\left(m\right)=M+\lambda l=50 \mathrm{N}$

Net acceleration of system $\left(a_{\mathrm{sys}}\right)=\frac{F}{m}=\frac{25}{50}=0.5 \mathrm{m} {\mathrm{s}}^{-1}$

Suppose Tension at a point connecting end of string with block is $T.$

From the $F.B.D.$ of block-

$\Rightarrow T=M{a}_{\mathrm{sys}}=48\times 0.5$

$\Rightarrow T=24 \mathrm{N}$

Hence, force acting on the block is $24 \mathrm{N}.$