Question

Three masses A, B & C revolve in the same plane about a centre O in the plane. The

radii of A, B & C are respectively 36cm, 50cm, and 30cm. Angle AOB = 90° and angle BOC
120°. The weight of C 25 KN. Determine the weight of A & B in order that the three masses
may balance.

Answer 1

Place A along the x-axis, B along the y-axis, and then C is 30 deg below the negative x-axis.

A = Cx to balance forces on the x-axis

Cx = -25 cos 30 = -21.65 kN

A = Ax = 21.61 kN balances forces in the x-direction

Likewise

Cy = -25 sin 30 = -12.5 kN

B = By = 12.5 kN balances forces in the y-direction

The length of the radii are not important (consider a force table)