Weight and gravitational force?

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Discussion Overview

The discussion revolves around the concepts of weight and gravitational force, particularly focusing on their definitions and relationships in the context of physics. Participants explore the equation w = Fg = mg and its implications for understanding mass and force.

Discussion Character

  • Conceptual clarification
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • One participant seeks a clear definition of weight and gravitational force, expressing confusion about the equation w = Fg = mg.
  • Another participant emphasizes the importance of using the correct unit for mass, identifying kilograms as the standard SI unit.
  • Some participants assert that weight is defined as the gravitational force acting on an object at the Earth's surface.
  • There is a discussion about whether weight and gravitational force are numerically equivalent, with some participants suggesting they are the same, while others clarify that weight is a force measured in Newtons.
  • One participant expresses uncertainty about the relationship between weight and gravitational force, asking if w = mg and Fg = mg are equivalent.
  • A later reply confirms that weight and gravitational force are indeed the same, leading to a participant expressing satisfaction with this clarification.

Areas of Agreement / Disagreement

There is a mix of agreement and confusion among participants regarding the definitions and relationships of weight and gravitational force. While some participants affirm that they are the same, others highlight the distinction between weight as a force and mass as a measure of matter.

Contextual Notes

Participants express varying levels of understanding about the units involved, particularly the distinction between Newtons and kilograms, and the implications of the equation w = Fg = mg. The discussion does not resolve all uncertainties regarding these concepts.

chemistry1
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Hi, I'm wondering if anybody could explain me the difference between these two concepts with a clear definition for someone who JUST began physics. Thanks ! Particularly, concerning this equation w=Fg=mg

Also, just to be sure I'm doing it in the right way, could I say that would be good

Ex : 15N=Fg=m*9,80N/Kg

re arrange like Fg=15N=m*9,80N/Kg

Would this be acceptable to solve for mass, knowing that these equations are equivalent ?
 
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Just make sure you have the right unit for mass. It looks like kg. in your description.
Weight is usually defined as the gravitational force on the surface of the earth.
 
mathman said:
Just make sure you have the right unit for mass. It looks like kg. in your description.
Weight is usually defined as the gravitational force on the surface of the earth.
Well, it's kg, isn't that the right unit ? And for weight and Fg of an object, it's exactly the same thing ?

If I have X N of weight, it means the gravitational force which gives that weight to the object will have the same numerical value ?

is this a good way of viewing it ? thanks
 
chemistry1 said:
Well, it's kg, isn't that the right unit ?
Yes, kg is the standard SI unit for mass.

And for weight and Fg of an object, it's exactly the same thing ?
No. Weight is a force; the standard SI unit for force is the Newton.

If I have X N of weight, it means the gravitational force which gives that weight to the object will have the same numerical value ?

is this a good way of viewing it ? thanks
No. Near the Earth's surface, a 1 kg mass will have a weight of W = mg ≈ (1 kg)*(9.8 N/kg) = 9.8 N.
 
Doc Al said:
Yes, kg is the standard SI unit for mass.


No. Weight is a force; the standard SI unit for force is the Newton.


No. Near the Earth's surface, a 1 kg mass will have a weight of W = mg ≈ (1 kg)*(9.8 N/kg) = 9.8 N.

Sorry if I misleaded you, I didn't mean that weight and Fg was in Kg. xD

It's just I don't see the relationship between weight and Gravitational force of an object.

Does w=mg and Fg=mg mean the same exact thing ? Could you tell it to me ? thanks again
 
chemistry1 said:
It's just I don't see the relationship between weight and Gravitational force of an object.
They are the same thing: the weight of an object is the gravitational force exerted on it by the earth.

Does w=mg and Fg=mg mean the same exact thing ?
Yes.
 
Doc Al said:
They are the same thing: the weight of an object is the gravitational force exerted on it by the earth.


Yes.

Ahhhhhhhhhhhhhhhhhh... Finally, that's what I wanted to read and be confirmed. Now, that makes me happy ! Thanks you and everyone else who posted !
 

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