Which statement about subatomic particles is not true?
a. protons and neutrons have almost the same mass.
b. protons and electrons have opposite charges.
c. unlike protons and electrons, neutrons have no charge.
d. protons and neutrons have the same charge.

Two charged particles, q1 and q2, are located on the x-axis, with q1 at the origin and q2 initially at x1 = 12.2 mm. in this configuration, q1 exerts a repulsive force of 2.62 µn on q2. particle q2 is then moved to x2 = 18.0 mm. what is the force (magnitude and direction) that q2 exerts on q1 at this new location? (give the magnitude in µn.)