What Went Wrong with My Calculation for Problem 14?

In summary, for Problem 11, the magnitude of the electric field at a point midway between two charges of 34.4*10^-9 C and 78.6*10^-9 C separated by a distance of 58.2 cm is 4698 N/C. For Problem 14, to find the magnitude of the electric force acting on the electron, you can use the formula F = ma, and for the magnitude of the electric field strength, you can use the formula L = F/q. However, when calculating the force in part A, you may have made a mistake in your calculation, leading to a wrong answer.
  • #1
mustang
169
0
Problem 11.
Find the magnitude electric field at a point midway between two charges of 34.4*10^9 C and 78.6*10^-9 C separated by a distance of 58.2 cm. Answer in N/C.
Note: Do i use coulomb's law? If so, when i multiply the constant to the quiotent is that my answer?

Problem 14.
An electron moving through an electric field experiences an acceleration of 6*10^3m/S^2.
a. Find the magnitude of the electric force acting on the electron. Answer in N.
Note: Do i use F=mass*acceleration?
b. What is the magnitude of the electric field strength? Answer in N/C.
What formula do I use?
 
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  • #2
E=qF will help u
F=ma will do
 
  • #3


Originally posted by mustang
Problem 11.
Find the magnitude electric field at a point midway between two charges of 34.4*10^-9 C and 78.6*10^-9 C separated by a distance of 58.2 cm. Answer in N/C.
Note: Do i use coulomb's law? If so, when i multiply the constant to the quiotent is that my answer?
Find the field from 1 then the field from the other then subtract.

field from first charge:
[tex]F = \frac{k q_1 q_2}{d^2}[/tex]

One of the charges isn't there so just divide it out.
[tex]\frac{F}{q_1} = \frac{k q_2}{d^2}[/tex]

[tex]\frac{F}{q_1} = \frac{(9x10^9)(34.4x10^-^9)}{0.291^2}[/tex]

[tex]\frac{F}{q_1} = 3656[/tex] N/C

field from second charge:
[tex]\frac{F}{q_1} = \frac{k q_2}{d^2}[/tex]

[tex]\frac{F}{q_1} = \frac{(9x10^9)(78.6x10^-^9)}{0.291^2}[/tex]

[tex]\frac{F}{q_1} = 8354[/tex] N/C

field at that point:
8354 - 3656 = 4698 N/C




Problem 14.
An electron moving through an electric field experiences an acceleration of 6*10^3m/S^2.
a. Find the magnitude of the electric force acting on the electron. Answer in N.
Note: Do i use F=mass*acceleration?
b. What is the magnitude of the electric field strength? Answer in N/C.
What formula do I use?

For question A:
You know the formula [tex]F = ma[/tex]. You know the mass of an electron and its rate of acceleration. Sub into find the force.

For question B:
The force is given by the field strength x charge. For field I'll just put L since I don't know what it should be.
F = Lq
L = F/q

You solved the force in part A and you know the charge of an electron.
 
Last edited:
  • #4
Sorry

I rechecked and for problem 11 it was 34.4*10^-9C.
 
  • #5
so the answer will be 4698 * 10^-9
 
  • #6
Question for problem 14.

I had a=6*10^3 and m=9.109*10^-31. I subsituted those values for ma in F=ma and got 5.4654*10^-27. When i posted the answer I got it wrong. What did I do wrong?
 

1. What is Coulomb's Law?

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

2. When should I use Coulomb's Law?

Coulomb's Law should be used to calculate the force between two charged particles when the distance between them is large enough that the effects of other forces, such as gravity, are negligible. It is also most accurate when dealing with stationary charges.

3. How do I apply Coulomb's Law?

To apply Coulomb's Law, you will need to know the magnitude of the charges involved, the distance between them, and the value of the Coulomb constant (k = 8.99 x 10^9 N*m^2/C^2). Simply plug these values into the equation F = (k*q1*q2)/r^2, where F is the force between the charges, q1 and q2 are the magnitudes of the charges, and r is the distance between them.

4. Can Coulomb's Law be used for both positive and negative charges?

Yes, Coulomb's Law can be used for both positive and negative charges. The force between two like charges (both positive or both negative) will be repulsive, while the force between two opposite charges (one positive and one negative) will be attractive.

5. Are there any limitations to Coulomb's Law?

Yes, there are limitations to Coulomb's Law. It assumes that the charges are point charges (infinitely small and concentrated) and that they are stationary. In reality, most charged particles have a finite size and are constantly in motion, which can affect the accuracy of the calculations. Additionally, Coulomb's Law does not take into account relativistic effects at very high speeds.

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