Idea 7of 7Builds onWhy the feather lagsA perfect draw
When the air wins
A skydiver falls through air for ages. Her speed?
Today you'll discover
- what a long fall through air does to the speed
- why the air's push back cannot keep growing
- the speed where a fall stops speeding up
Think firstA skydiver falls through air, second after second
She falls through air for a long time. What happens to her speed?
Decide first, then press Next. Watch the gap stop growing.
A large ball and a small ball falling through air, the small one lagging. After a prediction the frames advance: the lag grows, then the forces on the heavy ball are picked out as the air's push back catches up with the pull, and the steady speed is named. The last step moves the jump to the airless Moon and asks whether a terminal velocity is reached.
See the whole ideathe big idea and the key word, in one place
The big idea
Terminal velocity: air resistance matches the weight; speed holds.
Why it happensAir resistance grows with speed. Weight does not. So a fall through air always reaches the speed where the two match, and stays there.
Key word
- terminal velocity
- the constant velocity a falling object reaches when air resistance has grown to equal its weight, so the net force is zero
About this modelWithout air, every mass falls the same way; the lag appears only when air pushes back.
Without air, every mass falls the same way; the lag appears only when air pushes back.
Ready to use it?
- Explain why a falling object through air reaches a steady speed, and what sets that speed.