posted by Tory on .
A 0.32 kg meter stick balances at its center. If a necklace is suspended from one end of the stick, the balance point moves 39.0 cm toward that end. What is the mass of the necklace?
The net torque about the fulcrum point is zero, when balanced. That means the torque due to the weight of the necklace (in one direction) equals the torque due to the weight of the meter stick (in the opposite direction). The weight of the meter stick can considered to act at the center of mass of the stick.
Mstick*g*(39 cm) = Mnecklace*g*(11 cm)
Mnecklace = Mstick * 39/11
Solve for the mass of then neccklace. You already know Mstick = 0.32 kg