Why objects fall differently in air
Gravity accelerates every object, but air drag depends strongly on speed, shape and area.
1. Weight pulls downward
weight = mass × gravity
Near Earth, weight remains approximately constant during the fall.
2. Drag pushes opposite motion
drag = ½ × air density × drag coefficient × area × speed²
Doubling speed makes drag about four times larger.
3. Net force sets acceleration
net downward force = weight − drag
As drag grows, downward acceleration becomes smaller than gravity.
4. Terminal velocity
When drag equals weight, net force and acceleration are zero. Speed then remains constant.
Learning objectives
- Compare weight and air resistance.
- Explain area-to-mass effects.
- Recognize terminal velocity on a graph.
- Predict effects of density, shape and parachutes.
- Explain why vacuum removes falling differences.
Suggested experiments
- Set density to zero and confirm both objects land together.
- Increase Object B area without changing mass.
- Choose the parachute and compare before and after deployment.
- Stack coffee filters: mass rises faster than frontal area.