Question

A man standing on a road hold his umbrella at 30⁰ with the vertical to keep the rain away. He throws the umbrella and starts running at 10 km/hr. He finds that raindrops are hitting his head vertically, the speed of raindrops w.r.t. the moving man, will be

• A. $10/\sqrt{2}km/h$
• B. 5 km/h
• C. $10\sqrt{3}km/h$
• D. $5/\sqrt{3}km/h$

Answer 1

Answer: (C)

$10\sqrt{3}km/h$

Answer 2

Taking vertical components equation (i) gives

$v_{rg}\cos 30{^\circ} = v_{rm} = 20\frac{\sqrt{3}}{2} = 10\sqrt{3}km/hr$