Question

Rain is falling vertically downwards with a velocity of $3\text{km/hr}$. A man walks in the rain with a velocity of $4\text{km/hr}$. The rain drop will fall on the man with a velocity of

• A. 5 km/hr
• B. 4km/hr
• C. 1km/hr
• D. 3 km/hr

Answer 1

The correct option is A 5 km/hr


In the figure, CB represents velocity of rain, CA represents velocity of the man. To find relative velocity of the rain with respect to man we add a velocity having magnitude equal to that of man in opposite direction to the velocity of man. It has been depicted by line CD. Now rain has two velocities simultaneously with respect to man . Their resultant.
$R^2=4^2+3^2\Rightarrow R=5$
which gives us the value of relative velocity of rain.