Two stationary, positive, point charges that are originally separated by a distance of 6.00 cm experience a mutually repulsive force of magnitude 8.00 μN.  What will be the magnitude of the repulsive force between the two charges when their distance of separation is reduced to 1.50 cm?   a. 128 μN   b. 32.0 μN   c. 96.0 μN   d. 160 μN   e. 64.0 μN

Three charges are placed on a horizontal line. Charges q1 = +7 nC and q2 = -3 nC are fixed in place, with q2 2.0 m to the right of q1. Charge q3=+5 nC is in equilibrium but free to slide on the line (but not off of it.) a. Find the distance between q3 and q1 and whether q3 is to the right or left of q1. b. If q3 can move along the line away from its initial location, is the equilibrium stable or unstable? How did you decide? c. If q3 were were on a vertical line instead, so it could move up and down but not horizontally, would the equilibrium be stable or unstable for that motion? How did you decide? m

Red blood cells can often be charged. Consider two red blood cells with the following charges: -24.6 pC and +51.6 pC. The red blood cells are 3.58 cm apart. a) What is the magnitude of the force on each red blood cell? b) The red blood cells come into contact with each other and then are separated by 3.58 cm. What magnitude of force does each of the red blood cells now experience?

B Q3 d₁ d₂ d3 d4 Three point charges Q₁ = -2.64 nC, Q2 = 3.24 nC and Q3 = 3.45 nC are shown in the figure. The distance in the figure are: d₁ = 1.10 cm, d₂ = 1.47 cm, d3 = 1.54 cm and d4 = 1.32 cm. The figure is not to scale. Use k=8.99 × 10⁹ Nm²/C². (a) If a proton is released from rest at point *B, how fast is it moving when it is very far away from the three charges? VC = (b) How fast would the proton need to be moving very far away from the three charges to reach *B with a speed of 9.78 x 105 m/s? VD= (c) If an electron is released from rest very far away from the three charges shown, how fast would it be moving at *B? VE = (d) How fast must an electron be moving at *B to come to rest very far away from the three charges? UF =