Question

Two boys raising a load pull at an angle to each other. If they exert forces of 30 N and 60 N respectively and their effective pull is at right angles to the directions of the pull of the first boy, what is the angle between their arms? What is the effective pull.

Answer 1

F1 = 30 N
F2= 60N
resultant force = R

R = √F1² + F2² + 2F1F2 cos0

angle of the resultant force will be the force applied by first boy is 90

tan 90 = B sin 0/ A + B sin 0
infinity = B sin 0/ A + B sin 0
A + B cos 0 = 0
A = - B cosФ
cosФ= -A/ B
= -1/2
Ф= 120

so R = √30² + 60² + 2 x 30 x 60 x cos 120
R = 51. 96N