Question

a man standing on the road has to hold his umbrella at 30 degree with the vertical to keep the rain away,he thrws his umbrella and starts running at 10 kmhr.he finds the rain drops hitting him vertically. what is the speed of the rain drops with respect to road?

Answer 1

When the man is at rest w.r.t. the ground, the rain comes to him at an angle 30° with the vertical. This is the direction of the velocity of raindrops with respect to the ground.                 Here v→rg=velocity of rain with respect to the ground                   v→mg= velocity of the man with respect to the ground.                 and v→rm=velocity of the rain with respect to the man,                 We have v→rg=v→rm+v→mg                ......(i)                 Taking horizontal components equation (i) gives                 vrgsin30∘=vmg=10km/hr                 or  vrg=10sin30∘=20km/hr