Terminal Velocity
Drag grows as an object speeds up, so the resultant force shrinks and the acceleration fades to zero. From then on the object falls at a steady speed, which changes if its area or weight changes.
What a learner can do afterwards
- Sketches the velocity-time graph of a skydiver before and after the parachute opens, and explains each section
- States that terminal velocity happens when drag equals weight, not when the force disappears
- Predicts how a larger surface area or a heavier load changes the terminal velocity
1 · Read
Drag is the push of air or water against motion, always pointing the opposite way. It grows as you go faster. A skydiver speeds up at first because weight beats drag.
Terminal velocity arrives when drag has grown to equal the weight. The forces balance, the resultant hits zero, and the fall continues at a steady top speed. The forces never vanish; they cancel out.
A velocity-time graph tells the tale: a steep rise first, then flattening toward terminal velocity. When the parachute opens, drag leaps up, the graph dips, and a new lower terminal velocity takes over.
Area and weight reset the top speed. A larger surface area means more drag and a lower terminal velocity, while a heavier load with the same drag means a higher one. On the Moon, with no air, a feather and a hammer land together.
Drag grows until it balances weight, and from then on you fall steady.
More to read
5.2 Drag Forces
Drag is the resistance an object feels moving through air or water. It always pushes the opposite way to the motion, and it grows as the object goes faster. A skydiver speeds up at first because weight beats drag.
Terminal velocity arrives when drag has grown to equal the weight. The forces balance, the resultant hits zero, and the fall continues at a steady top speed. It never means the forces vanished, only that they cancel out.
5.1 Friction
Friction and drag are cousins that both fight motion. Friction acts where surfaces rub, while drag acts through fluids like air and water. Both turn motion into heat and both grow in ways you can predict.
The skydiver story uses the same ideas as a brick sliding down a ramp. Find every force, work out the resultant, and the motion follows. Bigger resistive forces always mean smaller acceleration for the same pull.
2.7 Falling Objects
Without air, everything falls together. A feather and a hammer dropped on the Moon hit the ground at the same time because only weight pulls them down. On Earth, air resistance spoils this neat result for light, floaty things.
A skydiver's velocity-time graph shows the whole tale. It rises steeply at first, then flattens as drag builds toward terminal velocity. When the parachute opens, drag leaps up, the graph dips, and a new lower terminal velocity takes over.
Explore more
2 · Watch
به انگلیسیTake it off screen
Where it sits
This opens up
Where this leads
Jobs that lean on this skill. Follow one to see everything it is built on.
8 questions wait behind this lesson, each with its answer explained. Every answer feeds the sky: stars light as they are learned, and dim when it is time to come back.