Question

A person is standing on road by holding an umbrella at right angle to the horizontal surface in order to protect himself from rain falling at a speed of 10 metre per second and where as the velocity of wind is zero. Suddenly wind begins to blow at a speed of 20 metre per second, towards 30 degrees South of West now what angle the person has to turn his umbrella in order to protect himself from rain.

Answer 1

Final Answer : theta such that
$\tan( \theta) = \frac{1}{2}$
from ground.

Steps and Understanding :
1) The person has to turn his umbrella in the resultant of velocity of wind which is flowing in horizontal plane and velocity of rain.

For Diagram and calculation see pic.

Answer 2

Explanation:

Before raining,

A person is standing on road by holding an umbrella at right angle to the horizontal surface in order to protect himself from rain falling at a speed of 10 m/s and where as the velocity of wind is zero.

After raining,

The wind begins to blow at a speed of 20 m/s, towards 30° south of west.

So,

The person has to turn his umbrella at 30° North of east in order to protect himself from rain.

Because angle of south of west = north of east = 30°