Why Does Your Weight Seem to Change in an Accelerating Elevator?

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Apparent Weight: Why the Scale Reading Changes in a Lift

Apparent Weight: Why the Scale Reading Changes in a Lift

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Mass m
Acceleration a
PHYSICS INSIGHTS

True weight is gravity's pull, mg; nothing the lift does changes it. A scale never measures gravity: it reads the normal force N it pushes up with, your apparent weight, what your legs feel.

Up is +. ΣF = N − mg = ma, so N = m(g + a): only a counts, never v. Speeding up going up, or slowing down going down: a > 0, N > mg, you feel heavier. Speeding up going down, or slowing down going up: a < 0, N < mg, lighter. Steady speed, up or down: N = mg, so a smooth ride feels like standing still.

At a = −g, N = 0: weightless. Gravity still acts; the floor just falls as fast as you do. Cut the cable and that is the fall, until the emergency brake grips the rails at +g: N = 2mg. You can set a from −g to +g: a floor can only push, and each trip slows as hard as it sped up.

Simulation by The Science Cube — https://www.thesciencecube.com/

Newton's Second Law: The Elevator Problem Interactive Simulation

Explore the physics of apparent weight with this interactive elevator simulation, designed for Class 11, Class 12, and AP Physics students. This tool visualizes exactly how a passenger's apparent weight (the normal force, N) changes relative to their true weight (F_g = mg) as the elevator accelerates. Watch real-time changes in the free-body diagram and live calculations of Newton's second law: N = m(g + a). Test different kinematic phases including upward acceleration, constant velocity, deceleration, and even free fall (a = -g) to understand why you feel heavier, lighter, or completely weightless in a moving elevator.

Why does the scale reading change in an accelerating elevator?

In short: A scale does not measure gravity. It reads the normal force N pushing up on you, which is your apparent weight. Your true weight mg never changes. Taking up as positive, N − mg = ma, so N = m(g + a). Only the acceleration changes the reading, never the velocity.

Common doubts

  • “Do I always feel heavier when the elevator moves up?” No. You feel heavier only while accelerating upward, meaning speeding up going up or slowing down going down. At steady speed, up or down, N = mg and the ride feels like standing still.
  • “Does my weight really change?” No. Your true weight mg stays the same. Only the apparent weight N changes.
  • “If the cable is cut, is gravity switched off?” No. Gravity still acts, but the floor falls as fast as you do. Then a = −g, N = 0, and you feel weightless.

Change the mass and acceleration in the simulation above, or press CUT CABLE, and watch the scale reading N respond.

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