Question

the resultant of two vectors p and q is R if q is doubled the new resultant is perpendicular to o then R equals :​

Answer 1

Answer:

R^2 = P^2 + Q^2 + 2 PQ cos theta -> 1

R^2 ' = P^2 + 4Q^2 + 4PQ cos theta -> 2

4Q^2 = P^2 + R' ^2 -> 3

=> Eqn 2 + 3

R'^2 = P^2 + P^2 + 4 PQ cos theta

2 PQ cos theta = - P^2 -> 4

From 1 & 4

R^2 = - 2PQ cos theta + Q^2 + 2PQ cos theta

R^2 = Q^2

R = Q

Q. E. D.