A) 10 km/hr
B) 20 km/hr
C) 30 km/hr
D) 40 km/hr
Correct Answer: B
Solution :
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 \[{{\overrightarrow{v\,}}_{rg}}=\]velocity of rain with respect to the ground \[{{\overrightarrow{\,v}}_{mg}}=\] velocity of the man with respect to the ground. and \[{{\overrightarrow{\,v}}_{rm}}=\]velocity of the rain with respect to the man, We have \[{{\overrightarrow{\,v}}_{r\,\,g}}={{\overrightarrow{\,v}}_{r\,m}}+{{\overrightarrow{\,v}}_{mg}}\] ......(i) Taking horizontal components equation (i) gives \[{{v}_{r\,g}}\sin \,30{}^\circ ={{v}_{m\,g}}=10\,km/hr\] or \[{{v}_{r\,g}}=\frac{10}{\sin 30{}^\circ }=20\,km/hr\]
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