Rain is falling vertically downwards with a speed of `4 km h^-1`. A girl moves on a straight road with a velocity of `3 km h^-1`. The apparent velocity of rain with respect to the girl is.

Options

A. `3 km h^-1`
B. `4 km h^-1`
C. `5 km h^-1`
D. `7 km h^-1`

Answer

C

Explanation

( c) `vec v_(r//g) = vec v_r + (-vec v _g)`
=`vec v_r - vec v_g = -4 hat j - 3 hat i`
`v_(r//g) = sqrt(v_r^2 + v_g^2)`
=`sqrt(16 + 9) km h^-1 = 5 km h^-1`.
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