Download Pre AP Physics - Spring Branch ISD

Pre AP Physics
Electrostatics WS
Coulomb’s Law
1. The electron and proton of a hydrogen atom are separated, on average, by a distance of about 5.3 x 10 -11 m.
Find the magnitudes of the electric force and the gravitational force that each particle exerts on the other. (mass
of electron = 9.109 x 10-31 kg; mass of proton = 1.673 x 10-27 kg)
2. A balloon rubbed against denim gains a charge of -8.0 µC. What is the electric force between the balloon and
the denim when the two are separated by a distance of 5.0 cm? Assume the charges are located at a point.
[230.4 N, attractive]
3. A small cork with an excess charge of +6.0 µC is placed 0.12 m from another cork which carries a charge of 4.3 µC.
a. What is the magnitude of the electric force between the corks? [16.125 N]
b. Is this force attractive or repulsive? [attractive]
4. Two identical conducting spheres are placed with their centers 0.30 m apart. One is given a charge of +12 x
10-9 C and the other is given a charge of -18 x 10-9 C. Find the electric force exerted on one sphere by the other.
[2.16 x 10-5 N, attractive]
b. The spheres are connected by a conducting wire. After equilibrium has occurred, find the electric force
between the two spheres. [9.0 x 10-7 N, repulsive]
5. Two electrostatic point charges of +60 µC and +50 µC exert a repulsive force on each other of 175 N. What is
the distance between the two charges? [0.393 m]
Equilibrium
6. Three charges lie along the x-axis. One positive charge, q1 = 15 µC, is at x = 2.0 m, and another positive
charge, q2 = 6.0 µC, is at the origin. At what point on the x-axis must a negative charge, q3, be placed so that
the resultant force on it is zero? [0.775 m from q2]
7. Problem 7: A charge of +2.00 x 10-9 C is placed at the origin, and another charge of +4.00 x 10-9 C is placed
at x= 1.5 m. Find the point between these two charges where a charge of +3.00 x 10 -9 C should be placed so
that the net electric force on it is zero. [0.622 m from q1]
8. Problem 8: A charge q1 of -5.00 x 10-9 C and a charge q2 of -2.00 x 10-9 C are separated by a distance of 40.0
cm. Find the equilibrium position for a third charge of +15.0 x 10-9 C. [0.245 m from q1]
9. Problem 9: A charge q1 of -6.00 x 10-9 C and a charge q2 of charge -3.00 x 10-9 C are separated by a distance
of 60.0 cm. Where could a third charge be placed so that the net Electric force on it is zero? [0.352 m from q1]
Electric Field Strength
10. Problem 10: A charge q1 = +7.00 µC is at the origin, and a charge q2 = -5.00 µC is on the x-axis 0.30 m from
the origin. Find the electric field strength at point P, which is on the y-axis 0.40 m from the origin. [2.72 x 105 N/C
at 66.605o]
11. Problem 11: A charge, q1 = 5.00 µC, is at the origin, and a second charge, q2 = -3.00µC, is on the x-axis
0.80 m from the origin. Find the electric field at a point on the y-axis 0.50 m from the origin. [1.66 x 105 N/C at
81.01o]
Mixed Practice
12. Object A has a positive charge of 6.0 x 10-6 C. Object B, carrying a positive charge of 3.0 x 10-6 C, is 0.30 m
away.
a. Calculate the force on A. [1.8 n, repulsive]
b. Calculate the electric force if the charge on B was negative. [1.8 N, attractive]
13. An object, A, with +6.0 x 10-6 C charge, has two other charges nearby. Object B, -3.00 x 10-6 C, is 0.040 m
to the right. Object C, +1.5 x 10-6 C, is 0.030 m below. What is the net force on A? [135.468 N at 41.634o]
14. Two positive charges of 6.0 µC are separated by 0.50 m. What force exists between the charges? [1.296 N,
repulsive]
15. A negative charge of -2.0 x 10-4 C and a positive charge of 8.0 x 10-4 C are separated by 30 cm. What is the
force between the two charges? [16000 N, attractive]
16. Object A has a charge of +1.8 µC and object B has a charge of -1.0 µC. They are 0.014 m apart. What is the
electric force between them? [82.653 N, attractive]
17. How far apart are two electrons, each with a charge of -1.6 x 10-19 C, if they exert a repulsive force of 1.0 N
on each other? [1.518 x 10-14 m]
18. A force of 4.4 x 103 N exists between a positive charge of 8.0 x 10-4 C and a negative charge of -3.0 x 10-4
C. What distance separates the charges? [0.701 m]
19. Two identical point charges are separated by a distance of 3.0 cm and they repel each other with a force of
4.0 x 10-5 N. What is the new force if the distance between the point charges is doubled? [1 x 10-5 N]
20. Two point charges are separated by 10.0 cm. If one charge is + 20.0 µC and the other is -6.0 µC, what is the
force between them? [108 N]
21. A charge of 4.0 x 10-5 C is attracted by a second charge with a force of 350 N when the separation is 10.0
cm. Calculate the size of the second charge. [-9.722 x 10-6 C]
22. A charge of +3.5 x 10-9 C and a charge of +5.0 x 10-9 C are separated by 40.0 cm. Find the equilibrium
position for a -6.0 x 10-9 C charge. [0.182 m from q1]
23. A charge of +1.5 x 10-9 C is placed at the origin, and another charge of +3.5 x 10-9 C is placed at x = 2.1 m.
Find the point between these two charges where a charge of +2.75 x 10 -9 C should be placed so that the net
electric force on it is zero. [0.831 m from q1]
24. A charge q1of -6.0 x 10-9 C and a charge q2 of -2.80 x 10-9C are separated by a distance of 60.0 cm. Find the
equilibrium position for a third charge of +11.0 x 10-9 C. [0.356 m from q1]
25. A charge q1 of +8.00 µC is at the origin and a charge q2 of -5.65 µC is on the x-axis 0.520 m from the origin.
Find the electric field strength at point P, which is on the y-axis 0.60 m from the origin. [1.487 x 105 N/C at
69.199o]
26. A charge q1 = +4.80 µC is at the origin and a charge q2 of -2.80 µC is on the x-axis 0.910 m from the origin.
Find the electric field strength at point P, which is on the y-axis 0.65 m from the origin. [9.200 x 104 N/C at
79.73o]
27. A charge q1 of -6.25 x 10-9 C and a charge q2 of -3.30 x 10-9 C are separated by a distance of 80.0 cm.
Where could a third charge be placed so that the net electric force on it is zero? [0.463 m from q1]