My weight increases, but does the scale say zero?

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Homework Help Overview

The discussion revolves around the concepts of mass and weight in the context of traveling near the speed of light and the effects of gravitational pull. Participants explore how these factors influence measurements on a scale in a weightless environment.

Discussion Character

  • Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • Participants question the relationship between mass and weight when gravitational forces are negligible, particularly in free space or while traveling at relativistic speeds. They discuss the implications of being "weightless" and the inability to use scales in such conditions.

Discussion Status

There is an ongoing exploration of the differences between gravitational pull and the effects of traveling at high speeds. Some participants provide insights into how mass is perceived from different frames of reference, while others reflect on practical examples, such as astronauts in orbit, to illustrate their points.

Contextual Notes

Participants note that the discussion is hypothetical and involves assumptions about traveling in space without gravitational influence. The complexities of measuring mass and weight in various frames of reference are acknowledged but not resolved.

javas1
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This is a general question, not requiring an equation.

If I travel near the speed of light, I know my mass will increase. I am assuming my weight will increase, but since there is little gravitational pull, since I am not near any large objects, then my scale would say near-zero, if I stepped on a scale?

Thank you.
 
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javas1 said:
This is a general question, not requiring an equation.

If I travel near the speed of light, I know my mass will increase. I am assuming my weight will increase, but since there is little gravitational pull, since I am not near any large objects, then my scale would say near-zero, if I stepped on a scale?

Thank you.

If there is no gravitation, and you are not in a spinning space craft, you can not step on the scale, but only keep it next to your feet, so as not let it fly away. You can not use scales in free space to measure mass.

You do not feel that your mass is more than normal when you travel with uniform velocity, as your velocity is zero in your own frame of reference.
Neither would any other scales, traveling with you, measure increase of your mass. Your mass is big for an observer who sees you traveling with speed near c.

ehild
 
ehild said:
If there is no gravitation, and you are not in a spinning space craft, you can not step on the scale, but only keep it next to your feet, so as not let it fly away. You can not use scales in free space to measure mass.

You do not feel that your mass is more than normal when you travel with uniform velocity, as your velocity is zero in your own frame of reference.
Neither would any other scales, traveling with you, measure increase of your mass. Your mass is big for an observer who sees you traveling with speed near c.

ehild

Thank you. That helps. Hypothetically speaking, if I stepped on a scale, then the scale would read zero, because there is no gravitational pull while traveling in a ship near the speed of light?
 
Gravitational pull and traveling near the speed of light are different things. If you travel in free space or just orbit around a planet or you are in a vehicle in state of free fall, you are "weightless" as both the scale and you move with the same velocity and acceleration. No need to travel near the speed of light.

Special relativity makes distinction of the mass measured from different frames of reference. If the observer measures the mass of an object that travels with some speed relative to him, he would measure the mass bigger than the "rest" mass. An observer traveling together with the object would measure the rest mass. If you travel alone in free space, far away from anything you even do not know your speed.

ehild
 
javas1 said:
Thank you. That helps. Hypothetically speaking, if I stepped on a scale, then the scale would read zero, because there is no gravitational pull while traveling in a ship near the speed of light?

Have you seen videos of astronauts in Earth orbit? Imagine one of them trying to step on a scale.
 
ideasrule said:
Have you seen videos of astronauts in Earth orbit? Imagine one of them trying to step on a scale.

That is what I cannot reconcile with. The astronauts in the space shuttle, when orbiting earth, would not be able to step on a scale.

That makes perfect sense.

Thank you again for your time.
 

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