Chapter 21 - Coulomb's Law - Questions - Page 624: 12a

In situation (a), the net force on the central proton is in the positive x direction. In situation (b), the net force on the central proton is in the positive x direction. In situation (c), the net force on the central proton is in the positive x direction. In situation (d), the net force on the central proton is in the negative x direction.

We can write an expression for the force between two charged particles: $F = \frac{q_1~q_2}{4\pi~\epsilon_0~r^2}$ In situation (1), the vertical components of the forces on the central proton due to the other particles cancel out. The horizontal components of the forces on the central proton are all directed in the positive x direction. Therefore, the net force is in the positive x direction. In situation (2), the vertical components of the forces on the central proton due to the other particles cancel out. The horizontal components of the forces on the central proton are all directed in the positive x direction. Therefore, the net force is in the positive x direction. In situation (3), the vertical components of the forces on the central proton due to the other particles cancel out. The horizontal components of the forces on the central proton due to the protons are directed in the positive x direction. The horizontal components of the forces on the central proton due to the electrons are directed in the negative x direction. Since the magnitude of the horizontal components of the forces due to the protons is greater than the magnitude of the horizontal components of the forces due to the electrons, the net force is in the positive x direction. In situation (4), the vertical components of the forces on the central proton due to the other particles cancel out. The horizontal components of the forces on the central proton due to the protons are directed in the positive x direction. The horizontal components of the forces on the central proton due to the electrons are directed in the negative x direction. Since the magnitude of the horizontal components of the forces due to the electrons is greater than the magnitude of the horizontal components of the forces due to the protons, the net force is in the negative x direction. In situation (a), the net force on the central proton is in the positive x direction. In situation (b), the net force on the central proton is in the positive x direction. In situation (c), the net force on the central proton is in the positive x direction. In situation (d), the net force on the central proton is in the negative x direction.