Does weight change in an elevator?

[pb23me]

Does an object gain weight?

When a person is in an elevator and the elevator begins to go up...Does the person actually gain weight? I know mass will not change obviously, but does the variable "g" vary due to acceleration?

 

[jtbell]

It depends on your definition of "weight." Most physics textbooks define "weight" as "gravitational force" (which equals mg near the surface of the earth). In this case your weight doesn't change in an accelerating elevator.

Some sources (including Hewitt's "Conceptual Physics") define "weight" as "what a bathroom scale (or other similar device) reads." In this case, your weight does change in an accelerating elevator.

 

[Gokul43201]

'g' is the acceleration due to gravity, which doesn't change when a person is in an accelerating elevator. What changes is the normal reaction, sometimes referred to as the apparent weight.

Note: posted simultaneously with jt

 

[SmokeyBastard]

apparent weight as in inertia ? Making your weight increase in the in the beginning of ascend .

 

[K^2]

Classically, no, as pointed out. But in the GR framework, if your coordinate system is attached to the elevator, yes, the weight increases.

 

[Champdx]

Should it be W=mg+ma?

 

[Dr Lots-o'watts]

Should it be W=mg+ma?

That would be the "apparent" weight mentioned by Gokul and jtbell.

 

[jewbinson]

In an exam question, they are unlikely to ask you, "When a person is in an elevator and the elevator begins to go up, does the person gain weight?" because this depends on your definition of weight.

They are more like to ask you, "If a person is standing on some weighing scales inside an elevator. The elevator starts from rest, goes upwards, stops, and comes back down, and stops again. Describe, at different stages, the readings on the scale (giving reasons for your answer)."