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Terminal velocity
Intermediate
Falling speed levels off when drag equals weight.
mg = kvA falling body speeds up until drag equals weight, then falls at constant terminal velocity. With drag kv: v_t = mg/k. Skydivers reach about 55 m/s belly-down and slow to about 5 m/s with a parachute.
A raindrop reaches terminal velocity in a few metres, which is why rain doesn't injure you.
At terminal velocity the acceleration is zero but gravity still acts.
In more detail
An object falling through air reaches terminal velocity when drag balances its weight, so its acceleration becomes zero and its speed stays constant.
Real-world uses
- Skydivers reach a terminal velocity of roughly 55 m/s in a belly-to-earth position.
- Raindrops fall at terminal velocity, which sets their size-dependent speed.
- Skydivers reach a terminal velocity of about 55 m/s in a belly-to-earth position, and the parachute lowers that speed for a safe landing.
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Frequently asked questions
Why does terminal velocity depend on shape?
Drag depends on the cross-section and shape, so a flatter body experiences more drag and a lower terminal velocity.
Can an object exceed terminal velocity?
Only temporarily, for example if it is launched downward or falls from a higher altitude into a region with different drag.
Why does a falling object stop accelerating?
Air drag grows with speed until it equals the weight, so the net force becomes zero and the velocity stays constant.
Related topics in Kinematics
Reaction time and braking · Non-uniform acceleration · Motion graphs from calculus · Two-dimensional motion · Projectile motion · Time of flight