Newton’s Cannonball

Fast enough to keep missing

An interactive lesson with 6 steps, about 5 minutes: you predict, drag and solve, with instant feedback on every answer. It runs in your browser and needs JavaScript.

What you’ll learn

• An orbit is free fall with enough sideways speed to keep missing the ground.
• Circular orbit speed: $v = \sqrt{GM/r}$, independent of the satellite's mass.
• Higher orbits are slower, and take longer.

Steps

1. Fire!
2. A perfect circle
3. Orbital speed
4. Higher orbit
5. The space station’s speed
6. Geostationary