Gravity Force Lab
Drag two masses and change their size to see how the gravity force depends on mass and distance.
Drag either mass along the ruler and change the masses. Every mass pulls on every other mass with the same size of force in opposite directions. Try the Earth and Moon, or the Sun and Earth, and see how far apart they must be to hold each other in orbit.
About the Gravity Force Lab
Free gravity force lab. Drag two masses and change their size to see how the gravity force depends on mass and distance. Drag, change the sliders and see the result live. No sign-up, works on phone and computer. Built for physics, the gravity force lab runs instantly in your browser: change a setting or drag an object and the result updates at once, so you learn by trying things out rather than only reading about them.
Drag two masses and change their size to see how the gravity force depends on mass and distance. Use it to explore physics ideas at your own pace, then check what you found against the key ideas further down this page.
How to use the Gravity Force Lab
- Use the controls to change Scenario, Mass 1, Mass 2, Separation, Force arrows, and more. The simulation reacts instantly.
- Pick an option such as Two balls (kg, m), Earth & Moon, Sun & Earth, Log scale to switch modes or load an example.
- Press "Reset" to start, reset or change what is happening.
- Where you see a glowing handle, object, weight or atom, drag it with your mouse or finger. Everything responds in real time.
- Watch the readouts and graphs update as you experiment, and compare what you see with the key ideas below.
Things to try
- Move the masses twice as far apart.
- Make one mass ten times bigger.
- Compare the two force arrows.
Key ideas you can learn
- F = G m₁ m₂ / r².
- Doubling a mass doubles the force.
- Doubling the distance makes the force four times smaller.
- The two forces are equal and opposite.
Where this is used in the real world
The same law explains tides, satellites orbits and the shape of galaxies.
Who is this simulation for?
Physics students in middle school, high school and first-year university, teachers who want a quick demonstration for the projector, and anyone revising for exams. It works well for flipped classrooms because students can explore before the lesson.
For teachers: project it on the board, let students predict what will happen, then run it together. For students: change one thing at a time and write down what changes.
Frequently asked questions
What is the inverse square law?
The force is proportional to 1 divided by the distance squared.
Why do we not feel the gravity of everyday objects?
G is extremely small, so the force between small masses is tiny.
Is the Gravity Force Lab free to use?
Yes. It is completely free, with no signup, no download and no ads inside the simulation. It runs in your web browser.
Does the Gravity Force Lab work on a phone or tablet?
Yes. It uses touch as well as the mouse, so you can drag objects with your finger. A larger screen makes the controls easier to see.