Newton's Law in Elevators
Apparent weight changes with acceleration.
About this topic
In a lift, the scale reading is the normal force, which gives your apparent weight. When the lift accelerates up, N = m(g + a), so you feel heavier; accelerating down, N = m(g - a), so you feel lighter; at constant velocity N = mg. In free fall N = 0, so you feel weightless.
Your actual weight does not change; what changes is the force the floor exerts on you. The key is the direction of acceleration, not the direction of velocity: a lift moving upward but slowing down accelerates downward, so you feel lighter. Always draw a free-body diagram and apply F = ma with the upward direction positive.
Example: a 60 kg person in a lift accelerating upward at 2 m/s² has N = 60 x 11.8 = 708 N, compared with 588 N at rest. If the lift accelerates down at 2 m/s², N = 60 x 7.8 = 468 N. Fast lifts and roller coasters create these sensations, and astronauts at launch feel several times their weight.
Misconception: a constant-speed lift, even a fast one, produces no change in apparent weight. Only the start and stop moments, when the velocity changes, create a different feeling.
Key ideas
- Accelerating up feels heavier
- Free fall feels weightless
- N = m(g + a)
Quick check
Use cases: where Newton's Law in Elevators helps
- Homework: review the key idea behind Newton's Law in Elevators before you start a problem set.
- Exam revision: use the quick check to test whether you can recall Newton's Law in Elevators without notes.
- Visual learning: play with the interactive lab to see how Newton's Law in Elevators changes when you adjust its inputs.
- Teaching a friend: explain Newton's Law in Elevators in your own words, then compare your version with the key ideas.
The same laws describe car crashes, sports, satellites and everyday machines.
Frequently asked questions
What is Newton's Law in Elevators?
Apparent weight changes with acceleration.
What will I learn in Newton's Law in Elevators?
Accelerating up feels heavier. Free fall feels weightless. N = m(g + a).
Is Newton's Law in Elevators part of Physics?
Yes. It is one of 150 Physics topics on LearnViz HighSchoolEdu, with 3 key ideas, a live animation and a quick check.
Does the Newton's Law in Elevators lab work on a phone or tablet?
Yes. The animation resizes to fit your screen and supports touch, so you can drag, tap and slide with your finger.
How should I study Newton's Law in Elevators?
Read the summary and key ideas first, play with the interactive lab to see the idea in motion, then answer the quick check. If you get a question wrong, go back to the key idea it tests.
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