Balancing Act: Torque and Levers
force times lever arm decides which way it turns
A lever balances when m₁r₁ = m₂r₂. Torque is force times lever arm, and net torque over moment of inertia gives angular acceleration.
Physics
Forces, oscillation, orbits, torque, waves and fluids.
force times lever arm decides which way it turns
A lever balances when m₁r₁ = m₂r₂. Torque is force times lever arm, and net torque over moment of inertia gives angular acceleration.
the water pushes up with the weight of what you displace
Archimedes: a body is pushed up by the weight of fluid it displaces, so it floats with ρ_object/ρ_fluid of its volume under. Boats and crates in games.
a sine-shaped pull back to the bottom, minus friction
A swinging weight pulled by sin θ: its period is only 2π√(L/g) for small swings, and damping decays the arc. Grapples, lamps and ropes in games.
ellipses, equal areas, and T² ∝ a³
Orbits are ellipses with the star at one focus, sweep equal areas in equal times, and have T² ∝ a³. Place planets on rails exactly with Kepler's equation.
small launch errors become a spread of landing spots
Repeat a launch with a little speed error and the landings form a distribution. Mean, spread and why R ∝ v² shifts the average: the maths of weapon spread.
constant sideways speed, steadily changing vertical speed
Launch angle, speed and gravity fully determine a ballistic arc: x moves at constant speed while y accelerates downward.
everything orbits the shared centre of mass
Two gravitating bodies circle their shared barycentre: radii split by mass, period set by total mass. Plus a stable n-body integrator for games.
air molecules shuffle back and forth, the pattern travels
Sound is a longitudinal pressure wave: frequency sets pitch and wavelength, amplitude sets loudness. The physics behind 3D audio, delay and Doppler.
pull back in proportion, bleed energy, push in rhythm
Hooke's law, damping and a periodic push: the forced oscillator behind springy cameras, wobbly UI and suspension, and why driving at ω₀ explodes.