Weight Scaling: Gravitational & Normal Force Balance

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Discussion Overview

The discussion revolves around the relationship between gravitational force, normal force, and how weight is measured, particularly in the context of a bathroom scale. Participants explore the implications of Newton's laws of motion in this scenario, questioning how weight is represented when forces are in equilibrium.

Discussion Character

  • Conceptual clarification
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • Some participants assert that gravitational force and normal force balance each other, leading to the equation Gravitational force + Normal force = 0, questioning how weight is measured under this condition.
  • Others propose that the bathroom scale measures the normal force, which equals the weight when in equilibrium, suggesting that the forces are not action/reaction pairs as per Newton's third law.
  • A participant mentions using a spring mechanism to measure weight, indicating that the force applied by the spring is proportional to its compression, though this does not directly address the equilibrium question.
  • Another participant clarifies that the downward gravitational force and upward normal force are not action/reaction pairs, emphasizing that their balance is a result of equilibrium, which relates to Newton's second law rather than the third.

Areas of Agreement / Disagreement

Participants express differing views on the interpretation of Newton's laws in relation to weight measurement and the forces involved. There is no consensus on how to reconcile the concepts of gravitational and normal forces with the operation of a bathroom scale.

Contextual Notes

Some assumptions about the definitions of forces and the conditions of equilibrium are not fully explored, and the discussion does not resolve the mathematical implications of the proposed equations.

DhruvKumar
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Every action has equal and opposite action.
There is gravitational force and it pulls us towards it center and A FORCE FROM EARTH is being applied on our body.This is supporting force or Normal force.

Weight is the force of gravity applied on our body by Earth and If Earth pulls by X Newton of energy then a force from Earth is also coming of X Newton.
when we stand on Bathroom Scale than our weight is shown by scale .
HOW?
Gravitational force+ Normal force = 0
Then how weight is scaled.
 
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DhruvKumar said:
Every action has equal and opposite action.
There is gravitational force and it pulls us towards it center and A FORCE FROM EARTH is being applied on our body.This is supporting force or Normal force.

Weight is the force of gravity applied on our body by Earth and If Earth pulls by X Newton of energy then a force from Earth is also coming of X Newton.
when we stand on Bathroom Scale than our weight is shown by scale .
HOW?
Gravitational force+ Normal force = 0
Then how weight is scaled.


I don't know how the bathroom scale works, but you can use a spring and see the length of compression and know your weight since the force applied by the spring is proportional to the compression length
 
Mr.louis please read my question and understand it ,then give any answer.

According to Newton's Third Law,
Gravitational force+ Normal force = 0
Then how weight is scaled. As we know Weight is Gravitational force applied on a body by earth.
 
DhruvKumar said:
Mr.louis please read my question and understand it ,then give any answer.

According to Newton's Third Law,
Gravitational force+ Normal force = 0
Then how weight is scaled. As we know Weight is Gravitational force applied on a body by earth.


Taking downward as positive
Your equation should be,
Gravitational force - Normal force = 0

As explained by Mr. Lois.
The spring in the scale is compress and the force is -kx.
It is scaled according to x.
 
DhruvKumar said:
According to Newton's Third Law,
Gravitational force+ Normal force = 0
The downward gravitational force (your weight) and the upward normal force are not Newton's third law 'action/reaction' pairs. They happen to add to zero because you are in equilibrium--not accelerating. This is an application of Newton's 2nd law, not the third.
Then how weight is scaled. As we know Weight is Gravitational force applied on a body by earth.
What the scale measures is the normal force it exerts. Which, in this case, happens to equal your weight.
 

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