One group approached their investigation by dropping a mass so it
fell vertically downward. They planned to measure the position of the
mass as it descended using a motion detector. They checked whether
the motion detector that they were using was sensitive enough to
capture the motion during the fall, and they were satisfied.
Given that they are measuring the motion (position, velocity, and

acceleration) of the mass, the students can only measure
gravitational potential energy and kinetic energy; any other form of
energy is undetectable. If they hope to see that energy is conserved
in this system, which of the following assumptions must be true (or
approximately true)?

Air Resistance is negligible

The initial vertical velocity of the mass is negligible.