What is the Net Force on Charges in a Line?

[Kali8972]

I'm having problems figuring this one out. Some guidance would be great! Thanks!

Particles of charge Q1 = +75 µC, Q2 = +44 µC, and Q3 = -80 µC are placed in a line (Fig. 21-46). The center one is 0.35 m from each of the others. Calculate the net force on each charge due to the other two. (Assume the positive direction is to the right.)




Net force on Q1

F1=242 N
F2=110 N

Net force = -242N + 110N = -132 N
(correct)



Net force on Q2

F1= 242 N
F2= 259 N

Net force = -242N + 259N = 17 N
(wrong, but why??)



Net force on Q3

F1= 110N
F2= 259N

Net force = 259N + 110N = 369 N
(wrong, but why??)

 

[El Hombre Invisible]

On your force on Q2, it should be +242N, not -242N, since Q1 is pushing Q2 to the right - i.e. in the positive direction. I also calculate F2 as 258 N, not 259 N.

On your force on Q3, it should be -110 N, since Q1 is pulling Q3 to the left - i.e. in the negative direction. Again, I got 258 N, not 259 N for F2.

 

[Kali8972]

thanks for your help!

 

[El Hombre Invisible]

Nooooooooooooooooooooot a problem!