Name: _______________________________
What Holds Our World Together – Practice
1. Of the charge Q initially on a tiny sphere, a portion q is to be transferred to a second,
nearby sphere. Both spheres can be treated as particles. For what value of q/Q will the
electrostatic force between the two spheres be maximized?
Before
After
q
Q-q
Q
r
r
2. What must be the distance between point charge q1 = 26.0 μC and point charge q2 = -47.0
μC for the electrostatic force between them to have a magnitude of 5.70 N?
3. In the return stroke of a typical lightning bolt, a current of 2.5 × 104 A exists for 20 μs.
How much charge is transferred in this event?
4. Two equally charged particles are held 3.2 × 10-3 m apart and then released from rest. The
initial acceleration of the first particle is observed to be 7.0 m/s2 and that of the second to
be 9.0 m/s2. The mass of the first particle is 6.3 × 10-7 kg.
A. What is the mass of the second particle?
B. What is the magnitude of the charge of each particle?
5. The charges and coordinates of two charged particles held fixed in an xy plane are q1 =
+3.0 μC, x1 = 3.5 cm, y1 = 0.50 cm, and q2 = -4.0 μC, x2 = -2.0 cm, y2 = 1.5 cm.
A. Find the magnitude and direction of the electrostatic force on particle 2 due to
particle 1.
B. At what x and y coordinates should a third particle of charge q3 = +4.0 μC be placed
such that the net electrostatic force on particle 2 due to particles 1 and 3 is zero?
Solutions:
1. 0.50
2. 1.39 m
3. 0.50 C
4. A. 4.9 x 10-7 kg
5. A. 35 N @ -10o B. x3 = -8.4 cm y3 = 2.6 cm
B. 7.1 x 10-11 C