Understanding Elevator Physics: Solving a Mass Discrepancy on a Bathroom Scale

[dragon513]

Q.1 You know your mass is 65kg, but when you stand on a bathroom scale in an elevator, it says your mass is 82kg. What is the acceleration of the elevator, and in which direction?

Hello there, for some reason I always found myself having trouble with elevator questions. Can you solve this problem and explain it briefly what's going on? I appreciate your kindness. Regards,

 

[Pengwuino]

We won't solve problems here. Have you ever been in an elevator? As it goes up in this problem, its accelerating upwards. So you have that force acting on you along with gravity. Gravity alone puts your "mass" (although its not mass actually) at 65 kg so gravity + the acceleration of the elevator will give you a different "mass".

 

[Mk]

Since the elevator is accelerating faster than you are, and inertia is wanting you to stay in the same state of motion you were in, you feel a force pushing you down. If you have ever ridden a roller coaster, accelerated quickly in a car, or just rode an elevator, you feel that force. This force, combined with the Earth's normal gravitational pull, will be pulling you down, while the elevator is going up.