In an experiment with a massless beam balance an unknown mass m is balanced by two known masses of 16kg and 4 kg as shown in figure. Find the value of the unknown mass m.

Question

G1 Physics · Accepted Answer

For a massless beam in equilibrium, clockwise and anticlockwise moments about the fulcrum are equal. Using the distances marked in the figure, 16g×(lever arm)=mg×(lever arm)+4g×(lever arm). Solving the moment equation gives m=8 kg.