# MCAT Physics Question — Neil Armstrong

• Reviewed By: Liz Flagge
• [raw]Neil Armstrong, standing on the Moon, is attempting to measure the acceleration due to gravity on the Moon. To do so, he is dropping a feather a distance of 2 meters and measuring the time it takes the feather to fall to the ground. Changing which of the following would change the measurements taken?

A) The mass of the feather

B) The shape and aerodynamic profile of the feather

C) Throwing the feather horizontally at 0º above the horizon rather than dropping it.

D) The radius of the moon.

Explanation

The gravitational acceleration between an object and a planet is given by:

g = GMplanet / r2

where G is the universal gravitational constant. Thus, changing the radius of the Moon would change the acceleration due to gravity and (D) is the right answer.

A: All objects fall at the same acceleration, regardless of their own mass.

B: There’s no atmosphere on the moon so the shape of the feather is irrelevant.

C: Horizontal motion is independent of vertical in projectile motion, so an object thrown straight out will hit the ground at the same time as an object dropped.

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