You are conducting an experiment inside an elevator that can move in a vertical shaft. a load is hung vertically from the ceiling on a string, and is stationary with respect to you. the tension in the string is measured to be 10% less than the weight of the load. no other forces are acting on the load. which of the following statements about the elevator are correct?
the elevator is an inertial frame of reference.
the elevator is not an inertial frame of reference.
the elevator may be at rest for the duration of the entire experiment.
the elevator may be moving at a constant velocity upward.
the elevator may be moving at a constant velocity downward.
the elevator must be accelerating

d. air pressure decreases as altitude increases.

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.