1. Coulomb’s Law – linear and 2 dimensional interactions
Forces and Fields Lesson 4

2. Background Information:
Charges are usually in the range of microCoulombs. Only lightning strikes have a charge of 1 or 2 coulombs.
The electron’s charge is so important it is called an elementary charge. Its symbol is “e” and is also on your formula sheet.

3. Net electrical force Determine the net force on object B.
always interpret this to mean that the
object in question is free to move and the
other objects are stationary.

4. Forces on B
Free body diagram

5. F C on B

6. F A on B

7. Fnet

8. AB down on B Example: Find the net electrical force on B. A
-2.0 x C
3.20 m
-1.5  C B C
4.1 m
-3.8  C
AB
down on B *

9. BC
left on B *

10. Draw Vector Diagram
3.05 x N
6.67 x N *

11. Example: Calculate the gravitational force between an electron and a proton placed 1.0 cm apart.*

12. Example: Calculate the electrical force between an electron and a proton placed 1.0 cm apart.*

13. Three point charges, A, B, and C, are arranged in a line as shown.
a. Determine the net electrostatic force acting on charge B.

14. b. The charge on object C is negative
b. The charge on object C is negative. Identify the sign of the charge (+ or -) on object i. A. ii. B.

15. 2 D Example:
Three point charged objects are arranged in a right angle as shown in the diagram.
a. The charge on object A is positive. Identify the sign of the charge (+ or -) on object
i. B. (negative)
ii. C. (negative)

16. Read WB p. 85-86 TB p. 532-6 Examples 10.3 to 10.6
b. Determine the net electrostatic force acting on charge B.
Read WB p TB p Examples 10.3 to 10.6
Do WB p ,8,10,14,16,18,19