If you walk 15m west and 7m east. what is your displacement?

If we consider our origin to be zero then if we walk 15m west then back 7m east our displacement would be the difference (since west and east are opposite directions to one another).

15m - 7m = 8m

And so, we are 8 meters away from our origin, thus our displacement is 8 meters.

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.

+15-35=-20

going in opposite directions