A rain drop is falling with velocity (2hati-4hatj)m/s. what should be the velocity of a man so that rain drops hit him with speed 5m/s?

1 Answer
Jul 8, 2017

A rain drop is falling with velocity (2hati-4hatj)m/s.
The velocity of the man will be in horizontal direction . So let the velocity of the man be ahati

So relative velocity of the rain drop w.r. to man will be (2-a)hati-4hatj.

By the given condition

abs( (2-a)hati-4hatj)=5.

=>sqrt( (2-a)^2+4^2)=5^2.

=>( (2-a)^2+4^2)=25.

=>(2-a)^2=9.

=>(2-a)=pm3.

So a=-1 or +5

So velocity of the man is -hati or 5hati m/s