Suppose you are far into deep space

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Discussion Overview

The discussion revolves around the concepts of acceleration, force, and the experience of weightlessness in various contexts, particularly in deep space and under different acceleration scenarios. Participants explore the implications of constant and varying acceleration, the role of gravitational and electromagnetic forces, and the subjective experience of acceleration.

Discussion Character

  • Exploratory
  • Debate/contested
  • Technical explanation

Main Points Raised

  • Some participants question whether one feels anything when accelerating at constant acceleration without physical contact, suggesting that if gravity is the cause, one would not feel anything.
  • Others propose that an accelerometer would read zero in a gravitational field since all parts of the body experience the same force, although some express uncertainty about time-varying fields.
  • There is a discussion about the definition of weight, with some asserting that one can never be truly weightless if weight is defined as the force of gravity, while others note that in free fall, one experiences apparent weightlessness.
  • Participants explore the idea of being accelerated by an electromagnetic field, with some questioning whether this is possible and how it relates to the experience of force.
  • The role of friction in the context of Maglev trains is debated, with some arguing that while electromagnetic fields cause acceleration, it is the friction that ultimately transfers this acceleration to the passengers.
  • There is contention over whether the experience of acceleration on a Maglev train can be considered as being accelerated without feeling a force, with differing opinions on the directness of the cause of acceleration.

Areas of Agreement / Disagreement

Participants express differing views on the experience of acceleration and the definitions of weight, with no consensus reached on whether one can be accelerated without feeling a force or the implications of electromagnetic acceleration.

Contextual Notes

Participants highlight the dependence on definitions of weight and the assumptions regarding the nature of forces involved in acceleration, which remain unresolved.

Forge
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You are accelerating at constant acceleration without anything physically touching you. Do you feel anything? What would an accelerometer read if the same force is applied to the accelerometer without anything physically touching the accelerometer? What would an accelerometer read if the no force is applied to the accelerometer and you are physically holding the accelerometer while you are accelerating at constant acceleration?

Now you accelerate at increasing acceleration without anything physically touching you. Do you feel anything? What would an accelerometer read if the same force is applied to the accelerometer without anything physically touching the accelerometer? What would an accelerometer read if the no force is applied to the accelerometer and you are physically holding the accelerometer while you are accelerating at increasing acceleration?
 
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If an inexplicable uniform gravitational field is giving me a weight, then I don't feel a thing because each element of mass in my body is subjected to proportional amount of force, and each bit of mass is accelerating due to this force by the same amount - there is no compression.

I don't see any reason the case would be different with a time-varying uniform gravitational field, but I never really thought about this before so I'm not certain.

I think an accelerometer would agree, since they are effectively measuring the same thing- proper acceleration.
 
Forge said:
You are accelerating at constant acceleration without anything physically touching you. Do you feel anything?
Depends on what is causing you to accelerate. If it is gravity, then no. Anything else must be physically touching you to accelerate you though.
What would an accelerometer read if the same force is applied to the accelerometer without anything physically touching the accelerometer?
Same answer: if it is gravity doing the accelerating, then it reads nothing.
What would an accelerometer read if the no force is applied to the accelerometer and you are physically holding the accelerometer while you are accelerating at constant acceleration?
Same answer.
Now you accelerate at increasing acceleration without anything physically touching you. Do you feel anything? What would an accelerometer read if the same force is applied to the accelerometer without anything physically touching the accelerometer?
Same answer.
What would an accelerometer read if the no force is applied to the accelerometer and you are physically holding the accelerometer while you are accelerating at increasing acceleration?
You can't accelerate something without applying a force to it.
 
So would you be technically correct in saying that you are weightless when you are in orbit with Earth despite that your weight causes you to stay in orbit?
 
It depends on what the definition of weight is.
If it is the force of gravity on an object then technically you can never be weightless.
If it is what can be measured on bathroom scales then you will have no weight in free fall.
Sometimes, in exam questions, an object in free fall is said to experience 'apparent weightlessness'
In an exam you would be expected to explain.
 
russ_watters said:
Depends on what is causing you to accelerate. If it is gravity, then no. Anything else must be physically touching you to accelerate you though.
How about being accelerated by an electromagnetic field?
 
ImaLooser said:
How about being accelerated by an electromagnetic field?
Can a person be accelerated that way?
 
The Maglev is a train propelled by electromagnetic effects. If you were on it I suppose you could say that electromagnetic fields were responsible for the acceleration you experience.
 
technician said:
The Maglev is a train propelled by electromagnetic effects. If you were on it I suppose you could say that electromagnetic fields were responsible for the acceleration you experience.

Wouldn't it be friction?

The electromagnetic fields would be responsible for accelerating the magnets under the train. But the friction between the magnets and the train is responsible for accelerating the train. The friction between your feet and the train is responsible for accelerating you.
 
  • #10
technician said:
The Maglev is a train propelled by electromagnetic effects. If you were on it I suppose you could say that electromagnetic fields were responsible for the acceleration you experience.

That's pretty indirect. What is causing your acceleration is the back of your seat. THAT's what is touching you.
 
  • #11
Indirect but not wrong
 
  • #12
technician said:
Indirect but not wrong

agreed
 
  • #13
Disagree. Two reasons:

1. The magnetic field accelerates the train. You are accelerated by the chair you are sitting in. "Would be responsible" is carefully selected wording to try to avoid this disconnect.
2. The question was asking how you can be accelerated without feeling a force. If you are on a maglev train that is accelerating, you most definitely feel a force.
 

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