In the Cavendish balance apparatus shown in Fig. 13.4, suppose that m₁= 1.10 kg, m₂= 25.0 kg, and the rod connecting the pairs is 30.0 cm long. If, in each pair, m₁and m₂are 12.0 cm apart center to center, find

(a) The net force

(b) The net torque (about the rotation axis) on the rotating part of the apparatus.

(c) Does it seem that the torque in part (b) would be enough to easily rotate the rod? Suggest some ways to improve the sensitivity of this experiment.

Figure 13.4: 

The principle of the Cavendish balance, used for determining the value of G. The angle of deflection has been exaggerated here for clarity.

Transcribed Image Text:

The deflection of the laser beam indicates how far the fiber has twisted. Once the instrument is Gravitation pulls the small masses toward the large masses, causing the vertical quartz fiber to twist. calibrated, this result gives a value for G. Mirror Laser beam The small balls reach a new equilibrium position when the elastic force exerted by the twisted quartz fiber balances the gravitational force between the masses. Laser mi F. m2 Quartz fiber Scale Large mass (m2) Small mass (m1)