A small body is projected with a velocity of `20.5 ms^(-1)` along rough horizontal surface. The coefficient of friction `(mu)` between the body and surface changes with time t (in s) as the the body moves along the surface. Find the velocity at the end of 4s in m/s

Explanation

Impulse `=intvecfdt=m(vecv_(1)-vecv_(1))`
`-mgxx"Area under" mu-t` graph `=m(V_(1)-20.5)`
`-mgxx[(1)/(2)(0.4+0.3)xx1+0.4xx2+(1)/(2)(0.4+0.2)+1]=m(V_(1)-20.5)`
`v_(1)=6m//s`