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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.

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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