Physic Labs

Newtonian mechanics

Gravitation and motion about the center of mass

Observe two-body orbits about their shared center of mass and how motion depends on mass ratio, separation, and speed. Track the bodies’ masses, separation, and mutual force, then check F=Gm1m2/r2F = Gm₁m₂/r².

Advanced

⚠ The orbits are a numerical simulation; do not drop objects from heights or create real impacts to test them.

Equipment

  • Two mutually gravitating bodies in three-dimensional space
  • m₁, m₂, r₀, relative-speed, and orbit-tilt sliders

Procedure

  1. Vary the two-body orbit

    Press Reset orbit to begin. Change m₁ and m₂ and observe both bodies orbiting their center of mass; the heavier body follows the smaller orbit. Adjust initial separation r₀ and reset to apply it, then vary the speed relative to circular to compare nearly circular, eccentric, or unbound paths. Drag to rotate the view and inspect the orbital-plane tilt. Compare the observed quantities with F=Gm1m2/r2F = Gm₁m₂/r².

  2. Check the center-of-mass position

    Pause and reset the orbit after changing m₁ and m₂. Compare each body's distance from the center of mass; check m1r1=m2r2m₁r₁ = m₂r₂ and observe that the heavier body follows the smaller orbit.

  3. Vary the initial speed

    Keep masses and initial separation fixed, then raise and lower relative speed around the circular-orbit setting. Classify the result as nearly circular, eccentric, or unbound and explain the role of initial conditions. Compare the observed quantities with F=Gm1m2/r2F = Gm₁m₂/r².

Simulation

Experiment history

Isaac Newton published Philosophiae Naturalis Principia Mathematica in 1687, uniting laws of motion with universal gravitation to explain terrestrial events and celestial motion in one framework. Building on planetary observations and Kepler's earlier astronomy, he argued that every body with mass attracts every other such body. In the two-body model, each body feels a gravitational force toward the other and both move about their shared center of mass. When their masses differ, the more massive body still moves but follows a smaller orbit. Newton did not use the modern concept of a gravitational field; the mathematics and interpretation of orbital motion were refined by later generations, especially in celestial mechanics.

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