Science Project:

Do Heavier Objects Fall Faster? Gravity in a Vacuum

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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!

Author: Justine Rembac
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