Mechanics
Terminal velocity
Watch speed level off well before landing, and acceleration (a) fall toward 0 as air resistance catches up with gravity.
Terminal velocity — interactive Mechanics simulation. Watch speed level off well before landing, and acceleration (a) fall toward 0 as air resistance catches up with gravity.
Terminal velocity
As a falling object speeds up, air drag grows until it balances weight. Acceleration then drops to zero and speed levels off.
Before terminal velocity, weight exceeds drag and the object accelerates. As speed increases, drag increases until net force is zero. The object then falls at a nearly constant terminal speed.
- F_net = mg − F_drag
- At terminal speed: a → 0
Investigation brief
Plan the question before you open the lab
The brief mirrors the prerendered page: driving question, competing predictions, variable roles, governing laws, setup, analysis and extension prompts remain visible and in this order.
Driving question
A skydiver falls through the air, which pushes back with a drag force that grows with speed. If the skydiver adjusts their body position to increase that air drag, does their steady falling speed (terminal velocity) end up higher, lower, or the same as with less drag?
Predictions to weigh
- More air drag gives a higher terminal velocity
- Terminal velocity is the same regardless of air drag
- More air drag gives a lower terminal velocity
Variable roles
What you set:
- Mass (kg)
- Air Drag
What you measure:
- Terminal Velocity (m/s)
- KE at Terminal Velocity (J)
How the investigation runs
- Open the Terminal Velocity preset. A skydiver (ball) starts near the top of the scene and falls under gravity while air drag acts on it.
- Confirm the speed probe is attached to the skydiver, then check its mass and the air drag (frictionAir) value in the Properties panel panel.
- For each row below, set the skydiver's mass and air drag in the Properties panel to match, run the simulation until the probe's speed reading stops changing (it will approach a steady value before the skydiver reaches the floor), and record that steady speed.
Governing equation
Newton's Second Law at Equilibrium — F = m·a
Net force equals mass times acceleration. As the skydiver speeds up, the upward drag force grows until it exactly balances the downward pull of gravity — net force (and therefore acceleration) drops to zero, and speed stops changing. That steady speed is the terminal velocity you measured.
Kinetic Energy — KE = ½·m·v²
Kinetic energy is one-half mass times speed squared. Once the skydiver reaches terminal velocity, this is the kinetic energy they carry for the remainder of the fall — energy that air resistance continuously removes as heat, keeping the speed constant.
What the printable worksheet asks students to work out
- For each row, multiply the terminal speed you measured by the air drag value and then by 60. You should land close to 9.8 × (1 − air drag), not 9.8 exactly. Why? The simulation applies drag once per frame rather than continuously, and that costs exactly one factor of (1 − air drag). What does the balance still tell you about the forces once the skydiver stops speeding up?
- Every row uses the same mass. Does mass appear anywhere in the relationship you found in the previous question? Based on your data, does a heavier skydiver reach a different terminal velocity than a lighter one in this simulation?
Where this shows up beyond the lab
- Real air resistance grows with the square of speed, not directly with speed, and its strength depends on the object's cross-sectional area and mass. Predict how a real skydiver's terminal velocity would change between a belly-down 'spread eagle' position and a feet-down dive — and why mass matters for a real skydiver even though it didn't in your data above.
- A skydiver opens a parachute, which sharply increases their air drag. Using the relationship you found, predict what happens to their falling speed right after the canopy opens, and explain why they don't instantly jump to the new terminal velocity.
- AP Physics 1 — Unit 2: Force and Translational Dynamics
- AP Physics C: Mechanics — Unit 2: Force and Translational Dynamics
- IB Physics — A.2 Forces and momentum
- General High School Physics — Forces & Newton's laws
- NGSS High School Physics — Forces and Newton's second law
- Welcome to Terminal Velocity
- Select the skydiver
- Press Play
- Speed plateaus
- Open the data
- You did it!
Open the interactive simulation to build the scene, press Play, and explore with live measurements and a guided tutorial.