Question #8328e

1 Answer
Feb 3, 2018

While running up the hill,his velocity vector is #(2i+3j) m/s#

And velocity of rain w.r.t the man is #-4j m/s#

So,velocity of rain w.r.t ground is #-4j+(2i+3j) m/s=2i-j m/s# (as velocity of rain w.r.t man = velocity of rain - velocity of man,so velocity of rain = velocity of rain w.r.t man + velocity of man)

While running down the hill,his velocity vector becomes #-(2i+3j) m/s#

So,velocity of rain w.r.t the man while going down is = velocity of rain - velocity of man #= 2i-j-(-2i-3j)=4i+2j m/s#

Hence the speed is #sqrt(4^2+2^2) m/s# i.e #sqrt(20) m/s#