A person of mass m stands on a scale in an elevator:
| Elevator Motion | Apparent Weight (Scale Reading) |
|---|---|
| At rest | mg |
| Moving up with constant v | mg |
| Accelerating upward (a) | m(g + a) |
| Accelerating downward (a) | m(g - a) |
| Free fall | 0 (weightless) |
| Decelerating while going up | m(g - a) |
| Decelerating while going down | m(g + a) |
Key insight: The scale reads the NORMAL force, not the weight. The normal force changes with acceleration, but weight (mg) remains constant.
Maximum tension in cable: When elevator accelerates upward: T = ( + )(g + a) String/cable breaks when T exceeds maximum capacity.