Question

A man sitting in a bus travelling in a direction from west to east with a speed of $40\text{km/h}$ observes that the rain-drops are falling vertically down. To another man standing on ground, the rain will appear

• A. To fall vertically down.
• B. To fall at an angle going from west to east.
  
• C. To fall at an angle going from east to west
  
• D. The information given is insufficient to decide the direction of rain.

Answer 1

The correct option is B To fall at an angle going from west to east.


A man is sitting in a bus and travelling from west to east, and the rain drops are appears falling vertically down.
Velocity of man, $\overrightarrow{v_m}=40\hat{i}$
$\overrightarrow{v_r}=$ Actual velocity of rain
Velocity of rain w.r.t. to moving man, $\overrightarrow{v_{r,m}}=-v\hat{j}$
Since, $\overrightarrow{v_{r,m}}=\overrightarrow{v_r}-\overrightarrow{v_m}\Rightarrow \overrightarrow{v_r}=40\hat{i}-v\hat{j}$

Hence, if the another man observes the rain from the ground, then he will find that actually rain falling with velocity $|\overrightarrow{v_r}|$, at an angle going from west to east.