Question

Two forces whose magnitudes are in ratio of 3:5 give a resultant of 35N. If the angle of inclination is 60°, calculate the magnitude of each force.

(a) 15N and35N

(b) 15N and 25N

(c) 10N and 15N

(d) 20N and 5N

This question was posed to me during an interview for a job.

Question is taken from Scalar and Vector in portion Laws of Motion of Engineering Physics I

Answer 1

Right choice is (b) 15N and 25N

Explanation: P = 3x and Q = 5x R = 35N θ = 120°

R = \(\sqrt{P^2 + R^2 + 2PQcosθ}\)

35 = 7x or x = 35/7 = 5

P = 15N Q = 25N.