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Applications of Coulomb’s Law. Physics 12. Coulomb Sample Problem. - PowerPoint PPT Presentation
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Applications of Coulomb’s Law
Physics 12
Coulomb Sample Problem
Three charges are arranged in a line; if the three charges are 15μC, -12μC and 18μC respectively. The distance between the first two charges is 0.20m and the second and third charges is 0.30m. What is the force experienced by the first charge?
Coulomb Sample Problem
What force is experienced by the remaining two charges?
Force (Vector) Addition
To add forces, resolve each force into its components and treat the forces in the x-direction and y-direction independently
Once you sum the x and y components, use Pythagorean Theorem and Trigonometry to resolve into a resultant force
Example
A point P has forces of 12.0N at 24.3°, 17.6N at 112°, 6.78N at 241° and 10.2N at 74.4°.Determine the resultant vector
25.5N, 81.4°
Coulomb’s Law and Vector Addition
When we consider an electrostatic system, we need to use Coulomb’s Law to determine the magnitude and direction of each force
Once the magnitude and direction of each force has been determined, then the vector sum can be completed
Coulomb’s Law in 2D
Three charges are arranged as follows; a -2.0μC is placed 4.0m due north of a 3.0μC charge and 3.0m due west of a 5.0μC charge. What is the force experienced by the -2.0μC charge?
Coulomb’s Law in 2D
NxF
r
qkqF
e
e
312
221
12
104.3
-2.0μC
3.0 μ C
5.0 μ C
4.0m
3.0m
NxF
r
qkqF
e
e
323
223
23
104.5
1
2
3
Coulomb’s Law in 2D
o
oo
233
18053
3.0 μ C2
NxF
NxF
NxF
NxF
NxF
NF
ye
ye
xe
xe
ye
xe
323
323
323
323
312
12
103.4
233sin104.5
102.3
233cos104.5
104.3
0
Coulomb’s Law in 2D
Use the x and y component data to determine the resultant force vector
NxF
NxNxF
NxF
NxNF
ey
ey
ex
ex
4
33
3
3
100.9
103.4104.3
102.3
102.30
oe
o
e
NxF
NxF
196,103.3
16
103.3
3
3
Practice Problems
Page 6406-10
Page 6421-7
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