1) an object has a charge of -2.3 μC. How many electrons must be removed so that the charge becomes +2.7 μC?

2) Two point charges are fixed on the y axis: a negative point charge q₁ = -26 µC at y₁ = +0.23 m and a positive point charge q₂ at y₂ = +0.31 m. A third point charge q = +8.7 µC is fixed at the origin. The net electrostatic force exerted on the charge q by the other two charges has a magnitude of 24 N and points in the +y direction. Determine the magnitude of q₂.

3) an electric field of 261,500 N/C points due west at a certain spot. What are the magnitude and direction of the force that acts on a charge of -6.35 µC at this spot?

4) A tiny ball (mass = 0.043 kg) carries a charge of -17.6 µC. What electric field (magnitude and direction) is needed to cause the ball to float above the ground?

5) the membrane surrounding a living cell consists of an inner and an outer wall that are separated by a small space. Assume that the membrane acts like a parallel plate capacitor in which the effective charge density on the inner and outer walls has a magnitude of 7.1 x  10^-6 C/m².

(a) What is the magnitude of the electric field within the cell membrane?

(b) Find the magnitude of the electric force that would be exerted on a potassium ion (K⁺; charge = +e) placed inside the membrane.

6) the drawing shows three point charges fixed in place. The charge at the coordinate origin has a value of q₁ = +8.20 µC; the other two charges have identical magnitudes, but opposite signs: q₂ = -5.30 µC and q₃ = +5.30 µC.

(a) Determine the net force (magnitude and direction) exerted on q₁ by the other two charges.

(b) If q₁ had a mass of 1.47 g and it were free to move, what would be its acceleration?