Teach lesson
Free Fall: measuring g and testing object effects
Students use the Free Fall remote lab to test h versus t^2, estimate gravitational acceleration, and decide when object shape affects real data.
Learning Outcomes
Collect reference fall-time evidence from the LabsLand Free Fall remote lab.
Use h = 1/2 g t^2 to estimate gravitational acceleration from height and time.
Compare a controlled height series with a controlled object comparison.
Write a claim-evidence-reasoning conclusion that distinguishes ideal models, real data, and uncertainty.
Student activity preview
Activity Content
Preview only. In a class session, students can fill in responses and submit their work to the teacher.
Understand the investigation
11 min
In this activity you will use a real remote lab. The lab lets you choose a ball and a release height, plays a recorded drop, and shows a fall time in seconds at the end. Your task is not to measure the height in the video: the height is selected in the lab interface and the time is copied from the final result.
Free fall means studying the motion of an object that falls because of gravity. In the ideal model, air resistance is ignored. In a real lab, air resistance and object shape can have a small effect, especially for large or light objects.
Vocabulary you will use:
- Height (h): vertical distance selected in the lab, in meters.
- Fall time (t): time shown by the lab after the drop, in seconds.
- Gravity (g): approximate acceleration of falling objects near Earth; it is usually close to 9.8 m/s^2.
- Air resistance: force from the air that opposes motion; it can make some objects take a little longer.
- Independent variable: what you deliberately change.
- Dependent variable: what you measure or record.
- Controlled variables: what you keep the same so the comparison is fair.
Model and variables
Model we will use
h = \frac{1}{2}gt^2 \quad\Rightarrow\quad g = \frac{2h}{t^2}
If two drops use the same ball, and one drop starts from a greater height, what should happen to the fall time in the ideal free-fall model?
Answer in 2 or 3 sentences. Explain why it is not a good idea to change height and object at the same time. Use the words independent variable, dependent variable, and controlled variable.
Open the lab from Teach
12 min
Remote lab workflow
Six-run plan
The lab is the main evidence source. Open the lab from the button in this activity, not from an external page. For each run, choose one configuration, let the drop finish, and copy one final time into the evidence table in the next section.
You will complete two comparisons:
1. Height series: the same metal ball at 1.10 m, 1.20 m, and 1.30 m.
2. Object comparison: the same height, 1.10 m, with the metal ball, yellow ball, white golf ball, and big hollow ball.
The metal ball at 1.10 m counts for both comparisons, so you need six rows in total.
Open the Free Fall lab
Open the Free Fall lab from Teach.
Choose the ball and height for the current row.
Start observing, then press the play button in the observation view.
When the experiment finishes, copy the fall time shown by the lab into the matching row of the data table.
Return to configuration and run the next row.
If Teach does not open the lab or the session does not offer the required licensed configurations, stop the lab portion and tell your teacher. Do not use an external page or another access mode to complete this activity.
Which plan best tests whether object choice matters?
Answer as a list of six rows. For each row, write the object, height, and whether it belongs to the height series, the object comparison, or both.
Record and process data
15 min
Before completing the table, copy only the final time shown by the lab for each run. Do not calculate distances from the video. In each row:
- Object, mass, and height describe the configuration.
- Fall time is copied from the final lab result, in seconds.
- t^2 is calculated by multiplying the time by itself.
- g estimate is calculated with g = 2h/t^2.
Free-fall evidence table
Complete one row per configuration. Keep the units: meters, seconds, seconds squared, and meters per second squared. Round t^2 and g to 2 or 3 decimals.
| Object | Mass g | Height m | Fall time s | t^2 s^2 | g estimate m/s^2 | Purpose |
|---|---|---|---|---|---|---|
Answer in one short sentence. Which units must height and time be in before you calculate g in m/s^2?
Write only your estimate of g for one table row, including the unit.
Explain the calculation for the estimate above. Include the row you used, the t^2 calculation, the substitution in g = 2h/t^2, and the final unit.
Look for patterns in the data
10 min
Before answering, separate the two comparisons. For the height series, use only the three metal-ball rows. For the object comparison, use only the four rows at 1.10 m.
Write the three data pairs for a graph of height versus t^2 using only the metal-ball rows. Use the format (t^2, h) and do not include measurements taken from the video.
Answer in 3 or 4 sentences and cite at least two numerical rows. Does the metal-ball height series approximately support that h grows with t^2?
Answer in 3 or 4 sentences. At 1.10 m, compare the four objects using fall times or estimates of g. Which object deviates most, and what possible physical explanation involves air resistance, shape, size, or uncertainty?
Make the scientific claim
9 min
If a fall time is measured too short, what happens to g = 2h/t^2?
Write a 6 to 8 sentence conclusion using the format claim, evidence, and reasoning. Include: an approximate estimate of g, two numerical data points from your table, a comparison between objects at the same height, and one limitation. Do not claim that this activity proves exactly that mass does or does not change gravity.
Debrief or extension
8 min
Optional answer in 2 or 3 sentences. If you had more lab time, what extra repeat or configuration would improve your conclusion? Explain which uncertainty it would reduce or which idea it would test.