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Do Heavier Objects Fall Faster? Gravity in a Vacuum

based on 12 ratings
Author: Justine Rembac
Topics: Ninth Grade, Physics

Do heavier objects fall faster? Newton observed the infamous apple falling from a tree, and drew important conclusions about the behavior of everyday objects under the force of gravity. In the case of a feather and a coin, one would believe that a feather will always fall more slowly to the ground, and the coin faster. However, as we will explore below, heavier objects do not always fall to the ground more quickly than lighter objects do! When dropped from the same height, objects fall to the earth at the same time when there is no major amount of air mass acting on them. Let’s discover why this is!

First, some background info: Mass, the quantity of matter an object contains, is (typically) constant in an object and does not change. In comparison, weight is the measurement of gravitational force being acted upon a particular object. Think about it this way: The mass of your body is the same on earth as it would be on the Moon, while your weight on earth would be much heavier here because the earth’s gravity is much stronger than the moon’s. This experiment aims to remove the variable of air mass acting on objects so we can measure the effect of gravitational acceleration produced by the earth’s gravity.

Materials

  • 1 vacuum pump with tube and end caps (available at scientific supply stores)
  • 1 feather
  • 1 coin
  • stopwatch

Procedure

  1. Assemble vacuum pump but do not turn it on.
  2. Leaving the pump lying horizontal, place a feather and a coin in top end of the pump.
  3. Turn the pump vertically and record your observations.
  4. Return the feather and the coin to the top of the vacuum pump.
  5. Seal both ends of the vacuum pump. Turn the pump on to remove the air.
  6. Now, turn the pump vertically and record your observations.

Observations & Results

The vacuum created an airless chamber for both items to fall freely. You should have noticed that the second time you dropped the feather and the coin, they both fell together at the same speed.

Why?

Gravitational acceleration was constant both times you dropped the items. The only difference from one trial to the next was the presence of air mass acting upon the feather: because the feather is an object of low density (it has a low ratio of mass to volume), the feather encounters more drag as it falls through the air. By removing most of the air, the feather should fall the same speed as the denser penny.

Conclusion

This experiment shows us that weight does not determine the rate at which something falls—only air resistance does. Try other things in the tube: a paper clip and a cotton ball, a crayon and a small leaf. Disregarding air resistance, can you believe a piano and pea would hit the ground at the same time if dropped from the same height? You bet!

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