View Single Post
Philip Wood
Philip Wood is offline
#2
Feb5-13, 12:07 PM
P: 865
Yes and Yes! If [itex]\textbf{F}_{i, j}[/itex] means the force that charged particle j exerts on charged particle i, then [itex]\textbf{F}_{i, j}[/itex] = [itex]\textbf{F}_{j, i}[/itex]. In other words the forces between the particles are equal and opposite.

For three particles,
the force on particle 1 is [itex]\textbf{F}_{1, 2}[/itex] + [itex]\textbf{F}_{1, 3}[/itex]
the force on particle 2 is [itex]\textbf{F}_{2, 3}[/itex] + [itex]\textbf{F}_{2, 1}[/itex]
the force on particle 3 is [itex]\textbf{F}_{3, 1}[/itex] + [itex]\textbf{F}_{3, 2}[/itex]

So the net force, that is the forces on all three particles added together, is zero, because
[itex]\textbf{F}_{1, 2}[/itex] = [itex]-\textbf{F}_{2, 1}[/itex] and so on.