1. A 75.0-kg box is falling with a constant velocity of -25.0 m/s. What is the force of air resistance?

Treating the box as a particle, there are two forces acting on it in opposite directions: the box's weight mg pulling it downward and the resistive force of the air pointing upward.

The box is falling at a constant speed, so by Newton's second law we have

mg - r = 0

where mg = (75.0 kg) (9.80 m/s²) = 735 N is the weight of the box and r is the magnitude of air resistance. So we have

r = mg = 735 N

it would be c. predictability

electric field is a function of 1/r^2

yes, the force per unit charge for a point charge is inverse square law.