If the force between two charges is F when the distance is d, what will the force between the two charges be if they were moved to a distance of 2d?

INT The surface charge density on an infinite charged plane is −2.0×10^−6 C/m^2 . A proton is shot straight away from the plane at 2.0×10^6 m/s . How far does the proton travel before reaching its turning point?

INT In a classical model of the hydrogen atom, the electron orbits the proton in a circular orbit of radius 0.053 nm. What is the orbital frequency in rev/s? The proton is so much more massive than the electron that you can assume the proton is at rest.

An electret is similar to a magnet, but rather than being permanently magnetized, it has a permanent electric dipole moment. Suppose a small electret with electric dipole moment 1.0×10^−7 C m is 25 cm from a small ball charged to +25 nC , with the ball on the axis of the electric dipole. What is the magnitude of the electric force on the ball?

Consider an oil droplet of mass m and charge q. We want to determine the charge on the droplet in a Millikan-type experiment. We will do this in several steps. Assume, for simplicity, that the charge is positive and that the electric field between the plates points upward. (c) A spherical object of radius r moving slowly through the air is known to experience a retarding force Fₔᵣₐ₉ = −6πηrv where η is the viscosity of the air. Use this and your answer to part b to show that a spherical droplet of density ρ falling with a terminal velocity vₜₑᵣₘ has a radius . r = √9ηvₜₑᵣₘ / 2pg

What is the distance between a$10\mu \mathrm{C}$ charge and a$24\mu \mathrm{C}$ charge if the magnitude of the force between them is $1.2\text{mN}$?

There is a $-4.00\text{nC}$charge at the origin. A $9.00\text{nC}$charge is on the x-axis at$x=2.00\mathrm{m}$. A$5.00\text{nC}$ charge is on the y-axis at$y=-1.00\mathrm{m}$. What is the total force on the$-4.00\text{nC}$ charge at the origin? Give your answer as a magnitude and an angle counterclockwise from the positive x-axis.