Calculating Electric Force: Coulomb's Law Example and Solution

In summary: Q1 x Q2 = K x F / d2 Since the force is given but the charges were not, i tried to swap them, resulting inQ1 x Q2 = K x F / d2 but it was incorrect
  • #1
deldel
6
0

Homework Statement


Two identical conducting spheres of charges 3q and -q attract each other with a force of 36 x 10-3N. When they are separated by a distance of 0.2 m. The spheres are brought into contact with each other and then separated by a distance of 0.1 m.

What is the magnitude of the electric force on each one exerts on the other?

Homework Equations

The Attempt at a Solution


I just need to make sure that i can get Q1 and Q2 correctly[/B]

So what i tried to do was rearrange the formula to fit the question by doing
Q1 x Q2 = k x f / d2

so, 9x109 x 36 x 10-3
(0.2)2

= 324 x 106
(2 x 10-1)2

= 324 x 108
2

= 162 x 108

so Q1 = 162 and Q2 is -54

I think its wrong, please can anyone check
 
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  • #2
deldel said:
So what i tried to do was rearrange the formula to fit the question by doing
Q1 x Q2 = k x f / d2
That rearrangement is not correct. Show your steps.
 
  • #3
What is the formula to find Q1 and Q2

how should i properly arrange it?
 
  • #4
deldel said:
What is the formula to find Q1 and Q2

how should i properly arrange it?
What formula did you begin with? It should be elementary algebra to rearrange it. So show your steps.
 
  • #5
i began with F = K x Q1 x Q2 / d2


since the force is given but the charges were not, i tried to swap them, resulting in

Q1 x Q2 = K x F / d2


but it was incorrect
 
  • #6
deldel said:
i began with F = K x Q1 x Q2 / d2


since the force is given but the charges were not, i tried to swap them, resulting in

Q1 x Q2 = K x F / d2


but it was incorrect
It's incorrect because your algebra is incorrect.

You can't just "swap" variables from one side to the other. Operations must be performed identically on each side of an equation to accomplish what you want.

Start again with the original equation. As a first step, multiply both sides by d2.
 
  • #7
Alright, Thank you sir.
 
  • #8
In addition, it is useful to keep the units in the equations. You would have noted the problem then because the units do not match any more.
 

FAQ: Calculating Electric Force: Coulomb's Law Example and Solution

What is Coulomb's law?

Coulomb's law is a fundamental law of physics that describes the electrostatic force between two charged particles. It states that the force of attraction or repulsion between two point charges is directly proportional to the product of their magnitudes and inversely proportional to the square of the distance between them.

What are the variables in Coulomb's law?

The variables in Coulomb's law are the magnitude of the charges, the distance between the charges, and the medium in which the charges are located. The force between two charges is directly proportional to the product of the charges (Q1Q2) and inversely proportional to the square of the distance (r) between them. The medium affects the force by altering the constant of proportionality.

How is Coulomb's law related to Newton's law of gravitation?

Coulomb's law and Newton's law of gravitation are similar in that they both describe the force between two objects. However, Coulomb's law applies to electrically charged particles while Newton's law of gravitation applies to objects with mass. Additionally, the force described by Coulomb's law is much stronger than the force described by Newton's law of gravitation.

What is the SI unit for electric charge in Coulomb's law?

The SI unit for electric charge in Coulomb's law is the Coulomb (C). This unit is named after the French physicist Charles-Augustin de Coulomb, who first described the law in the late 18th century.

Can Coulomb's law be applied to multiple charges?

Yes, Coulomb's law can be applied to multiple charges. The net electrostatic force on a charge due to multiple charges is equal to the vector sum of the individual forces exerted by each charge. This can be calculated by applying Coulomb's law to each pair of charges and then adding the resulting forces together.

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