Free body diagram of a person sitting on a wheeled chair

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Homework Help Overview

The discussion revolves around the mechanics of a person sitting on a wheeled chair and the forces involved when attempting to push the chair without contact with the floor. Participants explore concepts related to Newton's laws of motion and the implications of pushing against a chair while seated.

Discussion Character

  • Exploratory, Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • Participants discuss the feasibility of pushing the chair while seated and question the nature of forces involved, particularly in relation to Newton's third law. There are inquiries about the conditions under which the chair can be moved and the implications of being "floating" versus being in contact with the floor.

Discussion Status

The conversation is ongoing, with participants presenting differing views on whether pushing the chair is possible under the described conditions. Some suggest that if the person is floating, pushing the chair would result in no movement, while others argue from personal experience that movement is possible. The discussion reflects a lack of consensus on the mechanics at play.

Contextual Notes

Participants are considering scenarios where the person is either floating or strapped to the chair, which affects their interpretations of the forces involved. There is also mention of the difficulty in moving the chair against a surface like carpet, indicating practical constraints in the discussion.

Simfish
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So I am a person sitting on a chair that has wheels. Now, the question is - can I push the chair when I am sitting on the chair and have nothing to push against? [other than the chair]? Note that I have no contact whatsoever with the floor. From experience, I know I can. So why?

Whenever i try to push against the chair, according to Newton's 3rd Law, each force produces an equal and opposite force. So as I push against the chair, I exert a force, and it exerts an equal and opposite force on me. But I move along with the chair, so I must exert a second force on the chair, which is in the opposite direction as the direction of acceleration of the chair.

(a)
<--- (man on chair)
---->(chair on man)

(b)
--->(man's bottom on chair)
<---(chair on man)

such that man does not move with respect to the chair's reference frame. What about the outside world though? I know that the chair accelerates, so there must be a net force to the left.

The guy is in the middle, and he tries to push the chair to the left. I see three forces exerted. (a) is the man pushing chair left, the chair edge pushes the man right. Then the man's bottom and the chair have to push each other (b). Man pushes chair right, chair pushes man left. And what if you replace the man with say, a motor? The difference here would be that the motor would probably be a lot more attached to the bottom of the chair than the man would be.

So the question is - is the force in (a) greater than the force in (b) and why? Since if the force in (a) is greater than that in (b), then the chair will experience acceleration to the left, which is apparently what I experienced
 
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Now, the question is - can I push the chair when I am sitting on the chair and have nothing to push against? [other than the chair]? Nope.
Note that I have no contact whatsoever with the floor. Ok, so you and the chair are floating?
From experience, I know I can. If I understand you correctly, no you cant.

If you are not in contact whatsoever with the floor then you are floating and if you push on the chair you will float away from it. If you are strapped to the chair, nothing will happen.

If you are not floating, you are stuck in the chair, then you and the chair are one body in the action/reaction pair. What is the other body?
 
Simfishy said:
So I am a person sitting on a chair that has wheels. Now, the question is - can I push the chair when I am sitting on the chair and have nothing to push against? [other than the chair]? Note that I have no contact whatsoever with the floor. From experience, I know I can. So why?

Edit.. oops

it's the answer to this question
"then you and the chair are one body in the action/reaction pair. What is the other body?"
 
Last edited:
I'm trying to push the chair against the floor. But does this affect acceleration of the chair? I know from experience that I can move the chair against the carpet when strapped to the chair - but I have to struggle to move it (without touching anything)
 
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