Gravity Demonstration

Hands On: Gravity Demonstration


Big Idea:

Gravity pulls everything toward Earth at the same rate regardless of mass. What looks like "heavier things fall faster" is actually air resistance getting in the way.

Materials:

  • Two identical sheets of paper
  • Two identical plastic bottles (one full of water, one half-full or empty)
  • Optional: a chair or step stool for a higher drop



What to Do:

Step 1: Make Predictions

Before each drop, ask your learner which object will hit the ground first and why. Record predictions on the lab sheet, this is important. The point of the activity is to test the prediction, not just watch.


Step 2: The Paper Drop

Hold one flat sheet and one crumpled sheet at the same height. Drop both at exactly the same moment. Which lands first?


Step 3: The Bottle Drop

Hold the full bottle and the half-full bottle at the same height. Drop both at the same time. What happens?


Step 4: Try a Variation

If you want to go further, drop the crumpled paper and the full bottle at the same time. Do they land together? (They should, both are compact and face similar air resistance.)

Step 5: Discuss

  • Why did the crumpled paper fall faster than the flat paper? (Less surface area means less air resistance.)
  • Why did the two bottles land at the same time? (Same shape means same air resistance, and gravity causes all objects to accelerate at the same rate when air resistance is ignored.)
  • What would happen if you dropped both sheets of paper in a vacuum with no air?

What's Really Happening (Caregiver Explanation):

Gravity accelerates all objects at the same rate: 9.8 meters per second squared on Earth's surface. The only reason a flat sheet of paper falls slowly is that air pushes back against its large surface area. This is air resistance, not a difference in gravitational pull. Galileo is said to have demonstrated this by dropping cannonballs from the Leaning Tower of Pisa, showing that a ten-pound ball and a one-pound ball hit the ground at the same time. The result feels counterintuitive because our everyday experience constantly mixes up gravity and air resistance.

Digging Deeper:

Use the PhET 'Gravity and Orbits' simulator at phet.colorado.edu. Have learners adjust the mass of the Sun and Earth and observe what happens to the orbit. What happens if you make the Sun twice as massive? What if you move Earth twice as far away? They can also try the classic Galileo thought experiment in writing: if a heavy ball and a light ball are tied together and dropped, should they fall faster or slower than the heavy ball alone? What does the answer reveal about gravity?