In the Cavendish balance apparatus shown in the figure below, suppose that m 1 =
ID: 1555179 • Letter: I
Question
In the Cavendish balance apparatus shown in the figure below, suppose that m1 = 1.04 kg, m2 = 22.7 kg, and the rod connecting the pairs is 28.5 cm long.
(a) If, in each pair, m1 and m2 are 12.7 cm apart, find the net force.
N
(b) If, in each pair, m1 and m2 are 12.7 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?
Suggest some ways to improve the sensitivity of this experiment.
Explanation / Answer
a)
m1 = 1.04kg
m2 = 22.7kg
r = distance between the pair of masses = 12.7 cm = 0.127 m
gravitational force between the pair of masses is given as
Fg = Gm1 m2 /r2
Fg = (6.67 * 10^-11) (1.04) (22.7) / (0.127)^2
Fg = 9.76 * 10-8 N
b)
L = length of rod = 28.5 cm = 0.285 m
Net Torque = Fg x L = 9.76*10^-8*0.285 = 2.78x 10-8 Nm
c)
yes it would be enough
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No torque is very less