• Support PF! Buy your school textbooks, materials and every day products via PF Here!

Electrostatics calculation help

1. Homework Statement
What is the radius of the orbit of an electron travelling at 9.0E6 m/s around a zinc nucleus(which contains 30 protons)?


2. Homework Equations
F=(kQq)/r^2
F=QE
ac=v^2/r
Fnet=ma
3. The Attempt at a Solution
30 protons x 1.6E-19 = 4.8E-18 C
electron - 1.6E-19 C

F=ma
F=(9.11E-31)a
a=v^2/r
F=[(9.11E-31)(9.0E6)^2]/r
F=7.38E-17/r
(7.38E-17/r)=[(9.0E9)(1.6E-19)(4.8E-18)]/r^2
r=9.367E-11 m
 
One more quick question:

I know how to prove that if you move a charge twice as far away, the force will be one forth.
[(kQq)/r^2]/[(kQq)/(2r)^2]
(KQq4r^2)/(kQqr^2)
=4 times as weak

But what about if you increase the charge by twice as much, shouldn't both charges end up being 3/2 times as strong?

[(kQq)/r^2]/[(2kQq)/r^2] I end up getting 1/2???
 
Qucik Question, Plz Help@@@@@

1. Homework Statement
What is the radius of the orbit of an electron travelling at 9.0E6 m/s around a zinc nucleus(which contains 30 protons)?


2. Homework Equations
F=(kQq)/r^2
F=QE
ac=v^2/r
Fnet=ma
3. The Attempt at a Solution
30 protons x 1.6E-19 = 4.8E-18 C
electron - 1.6E-19 C

F=ma
F=(9.11E-31)a
a=v^2/r
F=[(9.11E-31)(9.0E6)^2]/r
F=7.38E-17/r
(7.38E-17/r)=[(9.0E9)(1.6E-19)(4.8E-18)]/r^2
r=9.367E-11 m

One more quick question:

I know how to prove that if you move a charge twice as far away, the force will be one forth.
[(kQq)/r^2]/[(kQq)/(2r)^2]
(KQq4r^2)/(kQqr^2)
=4 times as weak

But what about if you increase the charge by twice as much, shouldn't both charges end up being 3/2 times as strong?

[(kQq)/r^2]/[(2kQq)/r^2] I end up getting 1/2???
 

berkeman

Mentor
55,874
5,939
Okay, I unlocked your duplicate post and merged it here into this thread. Give me a minute to try to be helpful. Oh, and do not duplicate post again, okay?
 
Last edited:

berkeman

Mentor
55,874
5,939
Your radius calculation looks okay. Is it not matching the solution?
 
i was just unsure on my answer and wanted to get it checked. Also, I am just unsure on how to prove algebraically how a difference in charge of one particle will effect the overall charge between the two, like I solved algebraically for the distance increase between the two.
 

Related Threads for: Electrostatics calculation help

Replies
2
Views
2K
  • Posted
Replies
3
Views
672
  • Posted
Replies
5
Views
1K
Replies
4
Views
9K
  • Posted
Replies
14
Views
2K
  • Posted
Replies
0
Views
2K
  • Posted
Replies
1
Views
2K
Replies
5
Views
458
Top