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Homework for Coulomb\'s Law Lab 1. In this lab, we ignored the gravitational f i

ID: 1658602 • Letter: H

Question

Homework for Coulomb's Law Lab 1. In this lab, we ignored the gravitational f important. Now, we'll show that that assumption was justified. orce between the two spheres, assuming that the electric force was much more a) Estimate the masses of the two spheres, in kilograms. (You may ignore the masses of the supporting rods, ete) 6) For a forceration R 1 lorce between them. Show your work. (Note that your data table includes measured values of FE; you may use these. From rnysics 101, the gravitational force between two masses mi and m21s given by Fg 0 cm, calculate the ratio F,/Fe of the gravitational force between the two spheres to the e Gm1m2/R2 where G-6.67 × 10-11 Earth (i.e., the is Newton's constant. This is NOT the same as the gravitational force between each sphere and the sphere's weight)!) c) Explain why it was appropriate to ignore the gravitational force in this experiment. 2. In problem 1, you calculated the ratio of the forces for a specific separation, 10 cm. But in fact, this ratio is independent c the separation R. Explain why CONTINUED ON BACK 15

Explanation / Answer

Here Gravitational force between the spheres is ignored.

a)

Electric Force, F = 1/40(q1*q2/r2)

By Newton's second law, F=mass*acceleration

mass= Force/acceleration =1/40(q1*q2/r2)/acceleration

b)

The electric force between the two spheres at a distance 10cm apart is

Fe=1/40(q1*q2/r2)= 1/40(q1*q2/100)

0 is called the permittivity of free space . Its in SI units is 0= 8.854 × 10–12 C2 N–1m –2

Fe = -8.9x107(q1q2)Nm2

Gravitational force between the two spheres at a distance 10cm apart is

Fg=-Gm1m2/r2 = -6.67x10-11Nm2/kg2*m1*m2/100

= -6.67x10-11(m1m2)Nm2

Fg/Fe =-6.67x10-11(m1m2)Nm2/-8.9x107(q1q2)Nm2

= 0.749x10-18(m1m2/q1q2)

c) Here gravitational force is ignored because it is very smaller than electical forces between them