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# What is weight watch

1. Without using rather simplistic & counter intuitive terms (in my opinion, i.e. Weight is basically the force of gravity) .

What is weight?

What is it caused by?

Does it always act at the center of every object & why?
Why is every object on earth pulled towards the center of the earth?

What is the normal force, & why and how is it equal, of the same type of force, and opposite in direction to the other force? (Newton's Third Law) . And why is it perpendicular to the center of mass? (Not sure, is it actually perpendicular to the center of mass?, LOL, What is the center of mass?) .

2. I think weight is measured in newtons and is the mass (kg) multiplied by the gravitational field strength (which is 10 on Earth)
W =mg ?

That's the extent of my possibly wrong knowledge though
3. (Original post by surina16)
I think weight is measured in newtons and is the mass (kg) multiplied by the gravitational field strength (which is 10 on Earth)
W =mg ?

That's the extent of my possibly wrong knowledge though
Wait that actually does help. The 10 (or 9.81 to be approximately closer to the average) in g=9.81 m/s^2 is the gravitational field strength on earth? ?
4. The weight of an object is the force gravity has on it; this is why the same object would have a different weight on the moon compared to the Earth. The gravitational field strength of the Earth is 9.81 (g). Objects are 'pulled' towards the centre of the Earth due to its gravitational field.

The centre of mass is where all the mass of the objects can be considered to be 'concentrated'; if a force acts upon an object that seems to be 'balanced', it will move in one direction without rotation.
5. Good question but first we must ask.. What is life?
6. I guess you could explain the first 3 by saying gravity bends spacetime. more massive objects bend spacetime more than smaller ones.
7. (Original post by Paranoid_Glitch)
Wait that actually does help. The 10 (or 9.81 to be approximately closer to the average) in g=9.81 m/s^2 is the gravitational field strength on earth? ?
I'm afraid I'm not a great source of knowledge since I'm only in year 11
But isn't the gravitational field strength in N/kg?
8. (Original post by surina16)
I'm afraid I'm not a great source of knowledge since I'm only in year 11
But isn't the gravitational field strength in N/kg?
Yes it can be. But if you apply newton's second law (F=ma) then the newton=kgms^-2, so
9. (Original post by samb1234)
Yes it can be. But if you apply newton's second law (F=ma) then the newton=kgms^-2, so
Oh that makes sense, thanks!
10. (Original post by similarBlank)
what's that really think long thing between his legs?
11. (Original post by thefatone)
what's that really think long thing between his legs?
The chair leg
12. (Original post by Student403)
The chair leg
oh i thought it was his dingly dong
13. (Original post by thefatone)
oh i thought it was his dingly dong
If your dingly dong is silver and metallic...
14. (Original post by Student403)
If your dingly dong is silver and metallic...
perfect

15. (Original post by Student403)
If your dingly dong is silver and metallic...
He nicknamed it his 'Iron Man'.
16. (Original post by similarBlank)
He nicknamed it his 'Iron Man'.
17. What is weight? A force that mass experiences in a gravitational field in the context of comparatively low mass near a much larger mass.

What is it caused by? Being in a gravitational field.

Does it always act at the center of every object & why? No, it acts on the centre of mass the object which is the average position of each point particle weighted by their corresponding mass.

Why is every object on earth pulled towards the center of the earth? The earth is spherically symmetrical and its density changes as a function of distance from the center, so the center of mass is at the center. The direction of the gravitational force (the weight in this context) acts between the center of mass of the two masses.

What is the normal force, & why and how is it equal, of the same type of force, and opposite in direction to the other force? (Newton's Third Law) . And why is it perpendicular to the center of mass? (Not sure, is it actually perpendicular to the center of mass?, LOL, What is the center of mass?) . Physically there is no difference between for example you pushing against a wall and the wall pushing against you, so the forces are of the same magnitude. Perpendicular to the center of mass doesn't really make any sense, the center of mass as explained previously is just a position in space.
18. (Original post by Terry Tibbs)
What is weight? A force that mass experiences in a gravitational field in the context of comparatively low mass near a much larger mass.

What is it caused by? Being in a gravitational field.

Does it always act at the center of every object & why? No, it acts on the centre of mass the object which is the average position of each point particle weighted by their corresponding mass.

Why is every object on earth pulled towards the center of the earth? The earth is spherically symmetrical and its density changes as a function of distance from the center, so the center of mass is at the center. The direction of the gravitational force (the weight in this context) acts between the center of mass of the two masses.

What is the normal force, & why and how is it equal, of the same type of force, and opposite in direction to the other force? (Newton's Third Law) . And why is it perpendicular to the center of mass? (Not sure, is it actually perpendicular to the center of mass?, LOL, What is the center of mass?) . Physically there is no difference between for example you pushing against a wall and the wall pushing against you, so the forces are of the same magnitude. Perpendicular to the center of mass doesn't really make any sense, the center of mass as explained previously is just a position in space.
THANK'S i think i get it, mostly. Though i'm still not entirely sure what the center of mass is & why the normal force exists? (is it because the particles exert a force back up on the force being applied to it. If so, why?).
19. (Original post by Paranoid_Glitch)
THANK'S i think i get it, mostly. Though i'm still not entirely sure what the center of mass is & why the normal force exists? (is it because the particles exert a force back up on the force being applied to it. If so, why?).
Say you have body made up of three particles with different masses arranged in a triangle for example, intuitively you'd think that the center of mass of the body is somewhere in the middle of the three particles but also that it is closer to the particle of greatest mass (because most of the mass is concentrated there). This is true but more accurately the exact position (I assume you know about position vectors) of the center of mass is equal to the sum of each particle's position times their mass all divided by the total mass, which is called a weighted average. Obviously each particle has their own weight but their combined weight acts on the center of mass of the body.

The normal force exists on something for the same reason the force causing the normal force exists: you could equally say that for the example of someone pushing against a wall the wall is pushing against that person and the force from that person on the wall is the normal (or reaction) force.
20. (Original post by Terry Tibbs)
Say you have body made up of three particles with different masses arranged in a triangle for example, intuitively you'd think that the center of mass of the body is somewhere in the middle of the three particles but also that it is closer to the particle of greatest mass (because most of the mass is concentrated there). This is true but more accurately the exact position (I assume you know about position vectors) of the center of mass is equal to the sum of each particle's position times their mass all divided by the total mass, which is called a weighted average. Obviously each particle has their own weight but their combined weight acts on the center of mass of the body.

The normal force exists on something for the same reason the force causing the normal force exists: you could equally say that for the example of someone pushing against a wall the wall is pushing against that person and the force from that person on the wall is the normal (or reaction) force.
THANKS finally understand it.

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