Explain that gravity pulls all objects toward Earth, and use evidence from drop tests to show that shape and air resistance, not just weight, affect how fast something falls.
Gravity is a force that pulls every object toward the Earth. It is why things fall down instead of sideways or up, and why a thrown ball always curves back toward the ground. Gravity pulls on everything, whether it is a feather, a rock, or you.
A common idea is that heavier objects always fall faster, but that is not quite right. Two solid balls of different weight, dropped from the same height at the same moment, hit the ground at nearly the same time. What really slows a falling object down is air resistance, a kind of friction with the air, which affects light, wide, or spread-out objects, like a flat sheet of paper or a feather, much more than it affects a compact, heavy object.
Mastery looks like: They can predict and explain a falling-object result using both gravity and air resistance, not weight alone.
Common stumbles: Assuming heavier objects always fall faster in every case, without considering shape and air resistance.