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KCET · Physics · Motion In Two Dimensions

Rain is falling vertically with a speed of \(12 \mathrm{~ms}^{-1}\). A woman rides a bicycles with a speed of \(12 \mathrm{~ms}^{-1}\) in east to west direction. What is the direction in which she should hold her umbrella?

  1. A \(30^{\circ}\), towards east
  2. B \(45^{\circ}\), towards east
  3. C \(30^{\circ}\), towards west
  4. D \(45^{\circ}\), towards west
Verified Solution

Answer & Solution

Correct Answer

(B) \(45^{\circ}\), towards east

Step-by-step Solution

Detailed explanation

The given situation is shown below

Here, velocity of rain, \(v_{r}=12 \mathrm{~ms}^{-1}\)
and velocity of woman, \(v_{w}=12 \mathrm{~ms}^{-1}\)
The relative velocity of rain w.r.t. woman is
\(v_{r w} =\sqrt{v_{w}^{2}+v_{r}^{2}} \)
\( =\sqrt{(12)^{2}+(12)^{2}}=12 \sqrt{2} \mathrm{~ms}^{-1}\)
The direction in which the woman should hold her umbrella is
\(\sin \theta =\frac{v_{w}}{v_{r w}}=\frac{12}{12 \sqrt{2}} \\ \Rightarrow \theta =\sin ^{-1}\left(\frac{1}{\sqrt{2}}\right)=45^{\circ}, \text { towards east}\)