Question

a person is standing on road by holding an umbrella at right angle to the horizontal in order to protect himself from rain falling at a speed of 10m/s,and where as the velocity of wind is zero.Suddenly wind begins to blow at a speed of 20m/s,towards30 (degree) south of west.Now by 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.