Question

Two thin hollow plastic spheres, about the size of a ping-pong ball with masses (m1=m2= 0.008 kg) have been rubbed with wool. Sphere 1 has a charge q1= -9 × 10^-9 C and is at location < 0.39, -0.28, 0 > m. Sphere 2 has a charge q2= -2 × 10^-9 C and is at location < -0.31, 0.47, 0> m. It will be useful to draw a diagram of the situation, including the relevant vectors.

a/ What is the electric force (vector) exerted on q2 by q1? (in xyz vector form)

b/ What is the ratio of the magnitude of the electric force to the magnitude of the gravitational force?

c/ If the two masses were 2 times farther away (that is, if the distance between the masses were 2 ×|r→|), what would be the ratio of the magnitude of the electric force to the magnitude of the gravitational force now?

Answer 1

Solution) The electric force is given by

Fe = KQ1Q2/r^2

K = 9×10^(9)

Q1 and Q2 are charges

r is distance

The gravitatiinal force is given by

Fg = Gm1m2/r^2

G is gravitational constant

m1 and m2 are masses

r is distance