Question

A girl standing on road holds her umbrella at 45° with the vertical to keep the rain away. If she starts running without umbrella with a speed of $15\sqrt2$ $kmh^{–1}$, the rain drops hit herhead vertically. The speed of rain drops with respect to the moving girl is

• A. $30$ $kmh^{–1}$
• B. $\frac{25}{\sqrt2}$ $kmh^{-1}$
• C. $\frac{30}{\sqrt2}$ $kmh^{-1}$
• D. $25$ $kmh^{–1}$

Answer 1

Answer: (C)

$\frac{30}{\sqrt2}$ $kmh^{-1}$

Answer 2

From graph,

$V_{RG} =15\sqrt2tan⁡\;45\degree$

= $15\sqrt2$

= $\frac{30}{\sqrt2}$

Therefore, the correct option is (C): $\frac{30}{\sqrt2}$ $kmh^{-1}$