# A block is projected with speed 20m/s on a rough horizontal surface. The coefficient of friction between the surface varies with time as shown in figure. The speed of body at the end of 4 second will be

Eshan
3 years ago
Dear student,

Area under the$\mu -t$curve multiplied by$mg$will give the change in momentum in that time.

Hence$\Delta(mv)=m\Delta v=1.8mg$
$\implies \Delta v=1.8g=18m/s$
Hence final speed=$20m/s-18m/s=2m/s$