In a sublimation apparatus, the water pressure in the connected aspirator should be . A water pressure that is too low would the system, slowing or stopping the sublimation. In general, variations in water pressure could also .

A) The water should be well sealed by putting a water trap between the aspirator and the sublimator to avoid water backing up and filling the sublimator as a result of sudden pressure drop.

B) Variation in water pressure could cause water to back up and fill the sublimator.

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.