Question

A block of mass $5kg$ is placed on horizontal surface and a pushing force $20N$ is acting on back as shown in figure. If coefficient of friction between block and surface is $0.2$, calculate frictional force an speed of block after $15s$.

Answer 1

Given,

Coefficient of friction, $\mu =0.2$

Mass of block, $M=5kg$

Friction force, $F_r=\mu (mg+F\sin 45)=0.2\times (5\times 9.8+\frac{20}{\sqrt{2}})=12.63N$

Net force, $F_{net}=F\cos 45-F_r=\frac{20}{\sqrt{2}}-12.63=1.5N$

Acceleration, $a=\frac{F_{net}}{m}=\frac{1.5}{5}=0.3m{s}^{-2}$

Apply kinematic equation of motion

$V=U+at=0+\frac{1.5}{5}\times 15=4.5m{s}^{-1}$

Final velocity is $4.5m{s}^{-1}$