21.46 Find the magnitude and direction of the electrostatic force acting on the electron in the figure.

21.64 Two charged objects experience a mutual repulsive force of 0.10 N. If the charge of one of the objects is reduced by half and the distance separating the objects is doubled, what is the new force?

21.80 Two balls have the same mass of 0.681 kg and identical charges of 18.0 μC. They hang from the ceiling on strings of identical length as shown in the figure. If the angle with respect to the vertical of the strings is 20.0°, what is the length of the strings?

21.81 As shown in the figure, charge 1 is 3.94 μC and is located at x1 = −4.7 m, and charge 2 is 6.14 μC and is

at x2 = 12.2 m. What is the x-coordinate of the point at which the net force on a point charge of 0.300 μC is zero?

22.29 For the electric dipole shown in the figure, express the magnitude of the resulting electric field as a function of

the perpendicular distance x from the center of the dipole axis. Comment on what the magnitude is when x ≫d.

22.26 Two point charges are placed at two of the corners of a triangle as shown in the figure. Find the magnitude

and the direction of the electric field at the third corner of the triangle.

22.33 A thin glass rod is bent into a semicircle of radius R. A charge +Q is uniformly distributed along the upper

half, and a charge −Q is uniformly distributed along the lower half as shown in the figure. Find the magnitude and

direction of the electric field   (in component form) at point P, the center of the semicircle.