How Do Electrical Forces Interact in Physics Problems?

[seiferseph]

I have some more questions from a physics worksheet, this time on electrical forces. here are the questions and the answers i got, thanks in advance!

Questions:
http://i2.photobucket.com/albums/y15/seiferseph/electircalforces.jpg

Answers:

1) Fe = kQq/R^2, i get 3.6 x 10^10 N
2) a) Fg = GMm/R^2, i get 7.80 x 10^-47 N
b) Fe = kQq/R^2, using 1.6x10^-19 for both Q and -1.6x10^-19 for q, i get Fe = -8.86x10^-8 N
3) Q = n*e, Q/e = n. n = 2.5x10^19. i have a question though, can it be negative? (the charge is negative)
4) How do i do this one? is it just a simple ratio problem?
5) a) i calculated the force of each one seperately, i used 2*1.6x10^-19 for the charge of the middle one, because it has two protons.
F 1 on middle = k*q1*qmiddle/R^2 = 3.2x10-16
F 2 on middle = k*q2*qmiddle/R^2 = 1.44x10-15
and i get 1.76x10^15 N to the right
b) F = m*a, F/m = a, where m is 4*1.67x10^-27 = 2.6x10^11 m/s^2

thanks!

 

[OlderDan]

I have some more questions from a physics worksheet, this time on electrical forces. here are the questions and the answers i got, thanks in advance!

Questions:
http://i2.photobucket.com/albums/y15/seiferseph/electircalforces.jpg

Answers:

3) Q = n*e, Q/e = n. n = 2.5x10^19. i have a question though, can it be negative? (the charge is negative)
4) How do i do this one? is it just a simple ratio problem?
5) a) i calculated the force of each one seperately, i used 2*1.6x10^-19 for the charge of the middle one, because it has two protons.
F 1 on middle = k*q1*qmiddle/R^2 = 3.2x10-16
F 2 on middle = k*q2*qmiddle/R^2 = 1.44x10-15
and i get 1.76x10^15 N to the right
b) F = m*a, F/m = a, where m is 4*1.67x10^-27 = 2.6x10^11 m/s^2

thanks!

1) 2) Correct approach.. did not check your computations
3) The negative charge comes from negatively charged electrons. The NUMBER of electrons is positive.

4) Yes. You can find the charge to mass ratio for one electron.

5) a) Are these forces in opposite directions?
b) There is no b showing

 

[thepatientmental]

1) Your calculation for the electrical force between the two charges is correct. However, it is important to note the direction of the force, which would be repulsive in this case since both charges are positive. So the correct answer would be 3.6 x 10^10 N to the right.

2)a) Your calculation for the gravitational force is correct. However, it is important to note that this is a very small force due to the extremely small masses of the particles involved.

b) Your calculation for the electrical force is also correct. Again, it is important to note the direction of the force, which would be attractive in this case since one charge is positive and the other is negative.

3) Your calculation for the number of electrons is correct, and yes, the charge can be negative in this case since it represents the charge of an electron.

4) For this question, you can use Coulomb's Law to calculate the electrical force between the two charges. Simply plug in the values given for Q and q, and then solve for the force.

5)a) Your calculations for the electrical forces are correct. However, when adding them together, it is important to consider the direction of the forces as well. Since both forces are to the right, the total force would be 1.76 x 10^15 N to the right.

b) Your calculation for the acceleration is correct. However, it is important to note that this is an extremely high acceleration, which is not likely to occur in real-life situations.

Overall, your calculations and answers are correct. Just make sure to pay attention to the direction of the forces and to use the correct values for the charges in your calculations. Keep up the good work!