The Physics Inside an Elevator
Step into an elevator and you become a physics experiment. That strange heavy-then-light feeling is Newton's laws acting on your body in real time — and the machinery above the shaft is a masterclass in applied mechanics.
Apparent weight
A scale under your feet reads the normal force, not your true weight. When the elevator accelerates upward, the floor must push harder — N = m(g + a) — and you feel heavier. Accelerating downward, N = m(g − a) and you feel lighter. At constant velocity, acceleration is zero and you feel exactly your normal weight.
Counterweights and pulleys
Most elevators hang the car and a counterweight on opposite ends of steel cables over a sheave (a large pulley). The motor then only needs to overcome the difference in weight plus friction — a direct, money-saving application of pulley mechanics.
Acceleration limits for comfort
Elevator controllers cap acceleration around 1 m/s² and jerk (the rate of change of acceleration) even more tightly. Your inner ear is an accelerometer, and it complains loudly when these limits are exceeded — the same reason fast elevators still take a while to get going.
Regenerative braking
Modern elevators recover energy when a heavy car descends or a light car ascends, feeding electricity back into the building — the same regenerative principle as hybrid cars, applied to a vertical shaft.
Try this yourself
- If you get the chance, stand on a bathroom scale in an elevator and watch the reading as it starts moving up, cruises, and stops.
- Time an elevator between two floors and estimate its top speed from the floor-to-floor height.
- Look up your phone's accelerometer app and record the acceleration curve of one elevator ride.