What of the following is a constant for an object falling freely towards the earth?
A. Velocity
B. Potential Difference
C. Acceleration
D. Kinetic Energy
E. Momentum

This might be getting too technical, but if you consider terminal velocity, velocity would be constant in that case only. The easiest and most sensible answer is still acceleration. I have to remember, “Don’t read into the question too deeply.”

Well, potential difference is definitely changing:
potential difference = m * g * h
(h is height from the ground, and that is definitely changing)

and since potential is changing, kinetic energy is changing:
total energy = potential + kinetic
and total energy cant be changed unless an external force exists…so potential is getting smaller, therefore kinetic energy is getting bigger

and it cant be velocity…right? because kinetic energy is increasing.

Kinetic energy = .5 * m * v ^2
(kinetic energy is increasing, so velocity is increasing)

and since velocity is increasing, momentum sure cannot be a constant.

momentum = m * v

—-

therefore, its definitely acceleration that is the only constant.

It’s the acceleration due to gravity, which has a value 9.81 m/sÂ².

When in free fall, velocity changes when moving towards a gravity source, which also means the momentum changes. The energy changes as the object gathers speed, and because it comes closer, it loses potential energy.

This is the only one that is close to constant. Actually, it varies a little bit as the wind resistance increases with speed. Also, for something coming in from very far away, the gravity will change and therefore acceleration will change.

Well once the object reaches a certain point the velocity is constant.

This might be getting too technical, but if you consider terminal velocity, velocity would be constant in that case only. The easiest and most sensible answer is still acceleration. I have to remember, “Don’t read into the question too deeply.”

Well, potential difference is definitely changing:

potential difference = m * g * h

(h is height from the ground, and that is definitely changing)

and since potential is changing, kinetic energy is changing:

total energy = potential + kinetic

and total energy cant be changed unless an external force exists…so potential is getting smaller, therefore kinetic energy is getting bigger

and it cant be velocity…right? because kinetic energy is increasing.

Kinetic energy = .5 * m * v ^2

(kinetic energy is increasing, so velocity is increasing)

and since velocity is increasing, momentum sure cannot be a constant.

momentum = m * v

—-

therefore, its definitely acceleration that is the only constant.

It’s the acceleration due to gravity, which has a value 9.81 m/sÂ².

When in free fall, velocity changes when moving towards a gravity source, which also means the momentum changes. The energy changes as the object gathers speed, and because it comes closer, it loses potential energy.

Hence, acceleration is the only one left over.

C. acceleration

This is the only one that is close to constant. Actually, it varies a little bit as the wind resistance increases with speed. Also, for something coming in from very far away, the gravity will change and therefore acceleration will change.