Observations and results
Did both balls hit the ground at the same time?
You should have found that both balls hit the ground at roughly the same time. According to legend, this is what Galileo showed in 1589 from his Tower of Pisa experiment but, again, it's debated whether this actually happened. If you neglect air resistance, objects falling near Earth’s surface fall with the same approximate acceleration 9.8 meters per second squared (9.8 m/s2, or g) due to Earth's gravity. So the acceleration is the same for the objects, and consequently their velocity is also increasing at a constant rate. Because the downward force on an object is equal to its mass multiplied by g, heavier objects have a greater downward force. Heavier objects, however, also have more inertia, which means they resist moving more than lighter objects do, and so heaver objects need more force to get them going at the same rate.
More to explore
Elephant and Feather—Free Fall , from The Physics Classroom
Engines of Our Ingenuity: No. 166: Galileo's Experiment , from John H. H. Lienhard, University of Houston
Video: Fall of 2 Balls of Different Weights , from Matthias Liepe, Cornell University
What Goes Up, Must Come Down: Conduct Galileo's Famous Falling Objects Experiment , from Science Buddies
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