Does weight change in an elevator?

In summary, the weight of a person does not change in an accelerating elevator according to the classical definition of weight as gravitational force. However, according to some definitions, the apparent weight may change due to the normal reaction. In the GR framework, the weight may also increase due to the coordinate system attached to the elevator. In an exam question, the weight readings on a scale inside an elevator may vary depending on the stages and definitions used.
  • #1
pb23me
207
0
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?
 
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  • #2


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.
 
  • #3


'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
 
  • #4


apparent weight as in inertia ? Making your weight increase in the in the beginning of ascend .
 
  • #5


Classically, no, as pointed out. But in the GR framework, if your coordinate system is attached to the elevator, yes, the weight increases.
 
  • #6


Should it be W=mg+ma?
 
  • #7


Champdx said:
Should it be W=mg+ma?

That would be the "apparent" weight mentioned by Gokul and jtbell.
 
  • #8


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)."
 

1. Does an object gain weight when it is heated?

No, an object does not gain weight when it is heated. The weight of an object is determined by its mass, which remains constant regardless of temperature. However, when an object is heated, it may expand in size, but its mass remains the same.

2. Does an object gain weight when it is immersed in water?

Yes, an object will gain weight when it is immersed in water. This is due to the buoyant force of the water, which acts on the object and increases its weight. The amount of weight gained depends on the volume of the object and the density of the water.

3. Does an object gain weight when it is in motion?

No, an object does not gain weight when it is in motion. The weight of an object is independent of its velocity. However, the object may experience a change in weight if it is subjected to external forces, such as air resistance or gravitational pull.

4. Does an object gain weight when it is cut into smaller pieces?

No, an object does not gain weight when it is cut into smaller pieces. The total weight of the object remains the same, even if it is divided into smaller parts. This is because weight is a measure of the gravitational force acting on an object, which is determined by its mass, not its size or shape.

5. Does an object gain weight when it changes state? (e.g. from solid to liquid)

No, an object does not gain weight when it changes state. When an object changes from one state to another (e.g. from solid to liquid), its mass remains constant. However, the weight of the object may appear to change due to the difference in density between the two states. For example, an ice cube will appear to have less weight when it melts and becomes liquid, but its mass remains the same.

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