Air resistance slows moving things — Physics, 7–10 years
Air may be invisible, but it pushes against objects moving through it. The effect grows when an object is faster or presents a larger surface, which is why parachutes open wide.
The air pushes back
Air resistance is a push from air against a moving object. A flat sheet feels more resistance than a crumpled one because it meets more air. Resistance can slow an object, change its motion, or help it fall gently.
Why do parachutes work?
Without enough air resistance, a falling person would speed up for longer and land dangerously fast. A parachute spreads a large fabric surface through the air. The air pushes upward against it, reducing the falling speed to a safer value.
Two paper shapes
Drop one flat sheet and one equal sheet crumpled into a ball from the same height, 2 m. Both are pulled downward by gravity, but the flat sheet meets more air. It pushes against the air more strongly, so it usually takes longer to reach the floor than the compact ball.
Heavier is not always faster
It seems sensible that a heavier object must fall faster, because gravity pulls more strongly on it. That idea ignores air resistance. A heavy, compact object may fall quickly, but a wide, light object can be slowed greatly; shape and surface matter as well as weight.
Moving through air
Cyclists and runners bend their bodies to present less surface to the air, while parachutists spread theirs to get more resistance. Cars, planes and sports helmets are shaped to let air flow smoothly. These designs use the same effect, sometimes to reduce resistance and sometimes to increase it.
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