Drop objects from different heights, measure time-to-ground, verify g = 9.81 m/s², then add a drag coefficient and watch terminal velocity take over.
Open PHYSIX and drag a Circle body to the top of the canvas. Set its mass to 1 kg in the properties panel. Press Play and observe it accelerate downward.
Enable the Graph panel (G key) and plot velocity-y vs time. The slope of this line is g. Measure it: click two points on the graph and read off Δv/Δt.
Use the equation h = ½gt² to predict how far the object should fall in 2 seconds. Measure the actual displacement from the canvas ruler, then compare.
In the body properties panel, set Drag coefficient Cᴅ = 0.47 (a sphere) and Cross-sectional area = 0.05 m². Re-run and plot velocity vs time again. Notice the curve flattening out as it approaches terminal velocity.
Set mass to 0.001 kg (feather equivalent) and Cᴅ = 1.3. Drop it alongside the 1 kg sphere. Then reduce gravity to Moon levels (1.62 m/s²) and set Cᴅ = 0 for both. They land together — exactly as Apollo 15 demonstrated.