1. you and a friend are spending the weekend making up missed lab experiments. you are on to second semester material and are studying the electrostatic interaction of two charges. you notice that two charges are exerting a certain force on one another. if the distance between two electric charges doubles, then the force they exert on each other changes by how much? a) 4 times as large
b) 2 times as large
c) ½ as large
d) ¼ as large

D) ¼ as large

Explanation:

The magnitude of the electric force between two charges is

where

k is the Coulomb's constant

q1 and q2 are the magnitudes of the two charges

r is the separation between them

From the formula we see that the magnitude of the force is inversely proportional to the square of the distance.

In this problem, the distance is doubled:

So the new force will be

So the force will decrease to 1/4 of its original value.

air exerts forces on falling objects near earth’s surface.

explanation:

the term 'free falls' refer to object that are falling towards the earth, in a situation in which gravity is the only force acting on the object.

for an object in free fall, the acceleration is constant (g, the gravitational acceleration), and so the velocity of the object constantly increases.

for objects near earth's surface, there is always another force acting on the object: the resistance due to the air. this force is opposed to the direction of fall of the object, and it is proportional to the velocity of the object, so as the object falls down, this force increases up to a point when it balances the force of gravity, and the object continues its motion at constant velocity (called terminal velocity). since in this case gravity is not the only force acting on the object, we are not in a situation of free fall.