In the Cavendish balance apparatus shown in the figure below, suppose that m 1 =
ID: 1457415 • Letter: I
Question
In the Cavendish balance apparatus shown in the figure below, suppose that m1 = 1.15 kg, m2 = 24.9 kg, and the rod connecting the pairs is 29.4cm long.
(a) If, in each pair, m1 and m2 are 12.1 cm apart, find the net force.
N
(b) If, in each pair, m1 and m2 are 12.1 cm apart, find the net torque (about the rotation axis) on the rotating part of the apparatus.
N · m
(c) Does it seem that the torque in part (b) would be enough to easily rotate the rod?
Yes or No
Suggest some ways to improve the sensitivity of this experiment.
Explanation / Answer
a)
m1 = 1.15 kg
m2 = 24.9 kg
r = distance between the pair of masses = 12.1 cm = 0.121 m
gravitational force between the pair of masses is given as
Fg = Gm1 m2 /r2
Fg = (6.67 x 10-11) (1.15) (24.9) / (0.121)2
Fg = 1.305 x 10-7 N
b)
L = length of rod = 29.4 cm = 0.294 m
Net Torque = Fg x L = 1.305 x 10-7 x 0.294 = 3.84 x 10-8 Nm
c)
yes it would be enough