Question

Rain drops fall vertically at a speed of $20 \, m \, s^{- 1}$ . At what angle (in degree) do they fall on the wind screen of a car moving with a velocity $15 \, m \, s^{- 1}$ , if the wind screen is inclined at an angle of $23^\circ $ to the vertical? [ $\left.\tan ^{-1}(0.75) \approx 37^{\circ}\right]$

Answer 1

$tan\left(\right.90^\circ -\theta \left.\right)=\frac{20}{15}$
$\therefore cot\theta =\frac{20}{15}=\frac{4}{3}$
$\Rightarrow \, \theta =37^\circ $
$\therefore \, \phi=37^\circ +23^\circ =60^\circ $ (Angle made with the windscreen)