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Coulomb's Law (should be easy)

  • #1
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2

Homework Statement


Two equally charged particles are held 3.2*10^(-3)m apart and released from rest. The initial acceleration of the first is 7 m/s^2 and that of the second is 9 m/s^2.

If the mass of the first is m1= 6.3*10^(-7) kg, what are a) the mass of the second particle and b) the magnitude of the charge of each?



Homework Equations



F=ma
F=kq1q2/r^2


The Attempt at a Solution



I just need a kick in the right direction here. I am looking at a worked solution to the first part and they make the assumption

F1=F2 , thus, m1a1=m2a2

But, for some reason I am uneasy with this. Why are these two forces equal?

Sorry for the lame question... I am out of practice and am trying to do some review.

Thanks
 

Answers and Replies

  • #2
nrqed
Science Advisor
Homework Helper
Gold Member
3,567
189

Homework Statement


Two equally charged particles are held 3.2*10^(-3)m apart and released from rest. The initial acceleration of the first is 7 m/s^2 and that of the second is 9 m/s^2.

If the mass of the first is m1= 6.3*10^(-7) kg, what are a) the mass of the second particle and b) the magnitude of the charge of each?



Homework Equations



F=ma
F=kq1q2/r^2


The Attempt at a Solution



I just need a kick in the right direction here. I am looking at a worked solution to the first part and they make the assumption

F1=F2 , thus, m1a1=m2a2

But, for some reason I am uneasy with this. Why are these two forces equal?

Sorry for the lame question... I am out of practice and am trying to do some review.

Thanks
They form an action-reaction pair (Newton's third law). They must be equal!
 
  • #3
nicksauce
Science Advisor
Homework Helper
1,272
5
F = q1q2 /r^2

q1q2 is the same for both particles, as is r.
 
  • #4
3,003
2
They form an action-reaction pair (Newton's third law). They must be equal!
I guess I can live with that.
 

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