JEE Main 2022 · 27 Jun · Shift 1 · Physics Q32

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PhysicsSingle correct+4 / -1Question 32 of 90

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 her head vertically. The speed of rain drops with respect to the moving girl is :

30 kmh

^{-1}

\dfrac{25}{\sqrt2}

kmh

^{-1}

\dfrac{30}{\sqrt2}

kmh

^{-1}

25 kmh

^{-1}

Answer and worked solution

Official answer: C

Standing. The umbrella at 45° means the rain's horizontal and vertical speeds are equal.

Running. At $15\sqrt2$ km/h the rain falls vertically, so the horizontal speed is $15\sqrt2$ , and so is the vertical speed.

Relative speed = vertical component $=15\sqrt2=\dfrac{30}{\sqrt2}$ km h $^{-1}$ .

(C)

Topics:Relative velocity

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JEE Main 2022 · 27 Jun · Shift 1, Physics question 32