A man is walking on a horizontal road with a speed of 4km/hr finds that raindrops hitting his head vertically. When he decrease his speed to 3km/hr he finds that raindrops are hitting his head at an angle of 30 degrees with the vertical. The magnitude of velocity of the raindrops w.r.t ground will be…
Vm = 4i km/h
let Vr = ai+bj km/h
first case
Vrm =Vr-Vm= (a-4)i + bj
since rain is falling vertical then velocity along x axis must be zero
so, a-4=0
a=4
second case
Vm= 3 km/h
Vrm= i+ bj km/h
tan30°=1/√3=1/b
so b= √3 km/h
velocity of rain =√19 km/h