Mechanics
Free fall
Watch every mass fall at the same rate under gravity.
Drop objects from rest and measure free-fall acceleration, velocity, and displacement under gravity. Compare motion with and without air resistance in an interactive mechanics lab.
Free fall
In uniform gravity with no air resistance, all objects fall with the same acceleration g regardless of mass.
Galileo’s insight: mass cancels in F = ma when the only force is weight. Light and heavy objects released together hit the ground together in this idealized scene.
- y = y₀ + v₀t + ½gt²
- a = g (same for all masses)
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
Drop a light, a medium, and a heavy ball from the same height at the same time. Which one hits the ground first?
Predictions to weigh
- The heavier ball falls faster and lands first.
- All three fall at the same rate and land together.
- The lighter ball falls faster and lands first.
Variable roles
What you set:
- Mass (kg)
- Elapsed Time (s)
What you measure:
- Fall Speed (m/s)
- Momentum (kg·m/s)
How the investigation runs
- Open the free-fall preset. You should see three balls of different sizes lined up at the same height.
- Attach the height probe to the medium ball and confirm all three balls start at the same y-position.
- Run the simulation and use the stopwatch/frame counter to time each ball's fall.
Governing equation
Momentum — p = m·v
Even though all three balls share the same fall speed at a given time, their momenta differ because momentum scales with mass — this is why the heavy ball would do more damage on impact despite falling no faster.
What the printable worksheet asks students to work out
- Compare the fall speeds of the light, medium, and heavy balls at the same elapsed time. What do you notice?
- Using your data, compute the acceleration (Δspeed / Δtime) for each ball. How does it compare to g = 9.8 m/s²?
Where this shows up beyond the lab
- A feather and a bowling ball dropped in real air do NOT land together. What force, missing from this idealized sim, causes that difference?
- Astronauts on the Moon dropped a hammer and a feather and they landed together. Explain why the Moon is a better place than Earth to see this demonstration with real objects.
- AP Physics 1 — Unit 1: Kinematics
- AP Physics C: Mechanics — Unit 1: Kinematics
- IB Physics — A.1 Kinematics
- General High School Physics — Motion & kinematics
- NGSS High School Physics — Forces and Newton's second law
- Middle School Physical Science — Stored (potential) energy
- Middle School Physical Science — Energy in, energy out
- Which lands first?
- Test the mass
- Capture the fall
- Read the graph
- Explain your evidence
Open the interactive simulation to build the scene, press Play, and explore with live measurements and a guided tutorial.