CBSE Class 11-science Answered
Let us consider the following example to understand how to find the direction in which the umbrella should be held; when the velocity of rain as well as the person is given.
Q. Rain is falling vertically with speed of 30 m/s. A woman rides a bicycle with a spedd of 10 m/s in N to S direction. In which direction should she hold the umbrella?
A. Let vr (vector) be the velocity of rain and v (vector) be the velocity of woman. To the woman the rain will appear to come from the direction of vr - v (vector) . Therefore, the woman should hold the umbrella in the direction of
vr - v (vector) which is given by θ .
tan θ = v / vr = 10 / 30 = 1/3
i.e. she should hold the umbrella at an angle θ = tan -1 ( 1/3) south of vertical.