Question

(d) None of these
M
11. Three forces P, Q and R acting on a particle are in equilibrium. The angle between the
directions of P and Q is double between the directions of P and Ř. Then, R2 = ?-
(a) Q (R + P)
(b) 02 - PO​

Answer 1

Answer:

Square of Resultant R is R^2 = P^2 + Q^2 + 2PQ cos α,

α is the angle between P and Q.

tan θ = Q sin α / ( P + Q cosα), θ is the angle between R and P.

If Q is doubled , and if the angle between P and the new resultant S is 90 °,

tan 90 = 2Q sin α / ( P + 2Q cosα),=infinity.

Therefore, P = - 2Q cosα.

But R^2 = P^2 + Q^2 + 2PQ cos α,

R^2 = P^2 + Q^2 - P^2

R^2 = Q^2

R = Q ( in magnitude)