Question

Two forces have the same magnitude F. What is the angle between if there sum has a magnitude of (a) 2F (B) UNDERROOT 2F (c) 0

Answer 1

The forces are perpendicular. That is angle between them is 90 degrees.

It can be found by parallelogram law of vector addition.

In this case when you put Q=P ,R= root2 P and theta=ø

You get 2P^2 cos ø=0

Which implies cos ø=0 therefore ø=90 deg.

In simpler terms you can imagine a sqaure of side P and Resultant is given by the diagonal according to Parallelogram law. The length of diagonal will be root2 P by Pythagoras theorem.

The angles in a sqaure are right angles which again gives you the answer.