Gravity Simulator
Classroom worksheet · Interactive simulation: https://lkforge.com/tools/physics/orbit-simulator/
Name: Date:
Learning objectives
- Apply Newton's law of gravitation to orbital motion.
- Relate orbital speed and radius.
- Recognize Kepler's laws in the simulated orbits.
Variables to change
- Mass of central body
- Initial speed
- Initial position
- Number of bodies
Procedure
- Place one planet and give it a speed that produces a near-circular orbit.
- Reduce the speed and observe the orbit shape; then increase it.
- Increase the central mass and observe the effect on the orbit.
Observations
Note how orbit shape (circle, ellipse, escape) changes with initial speed and central mass.
Questions
- What shape is a bound orbit in general?
- How does gravitational force depend on distance?
- What happens if the initial speed is too high?
- State Kepler's second law and what it implies about speed.
- How does increasing the central mass change a stable orbit at fixed radius?
Answer key (instructors)
- 1. An ellipse, with the central body at one focus (a circle is the special case).
- 2. It follows an inverse-square law: F = G·m₁·m₂/r².
- 3. The object escapes on an unbound (parabolic or hyperbolic) path once it exceeds escape velocity.
- 4. A line from the planet to the star sweeps equal areas in equal times, so the planet moves fastest at closest approach (perihelion).
- 5. It increases the required orbital speed; stronger gravity demands faster motion to stay in orbit.
Gravity provides the centripetal force that holds bodies in orbit. The inverse-square law yields elliptical bound orbits (Kepler’s first law) and equal-area sweeping (second law). Too much speed and a body escapes; more central mass demands faster orbits.