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g is the strength of gravity

g is the strength of gravity - Physics Forum

g is the strength of gravity - Physics Forum. Discuss and ask physics questions, kinematics and other physics problems.


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  #1  
Old 09-12-2005, 12:18 PM
Don1
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Default g is the strength of gravity




g is the _strength_ of gravity, but what is the force of gravity?

Don

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  #2  
Old 09-12-2005, 01:12 PM
Sam Wormley
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Default g is the strength of gravity

Don1 wrote:

See: [Only registered users see links. ]
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  #3  
Old 09-12-2005, 07:11 PM
PD
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Default g is the strength of gravity


Don1 wrote:

Depends on what you mean by "strength of gravity".

The force of gravity is usually given in the Newtonian approximation as
a force between two objects. Let's call the mass of one object M and
the mass of the other object m, and let's say the distance between
their centers is r. Then the force is

F = G*M*m/r^2.

When one of the objects is the Earth and the other object is
comparatively small and close to the surface of the Earth, then M is
Mearth and r is Rearth, and this becomes

F = G*Mearth*m/Rearth^2

But let's pull out everything that doesn't have to do with the other
object m and put it in parentheses (at the risk of causing you some
algebraic alarm).

F = (G*Mearth/Rearth^2)*m

Running the numbers for G, Mearth, Rearth, we find out that
G*Mearth/Rearth^2 = 9.8 m/s^2, so we can say

F = m * (9.8 m/s^2)

Oh, heck that's still too long. Let's just write this as

F = mg.

PD

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  #4  
Old 09-13-2005, 09:00 PM
Double-A
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Default g is the strength of gravity


Don1 wrote:


Is that a trick question Don?

Double-A

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  #5  
Old 09-13-2005, 10:25 PM
Don1
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Default g is the strength of gravity

Double-A wrote:

Nope. We know that all bodies on Earth gravitate toward Earth's center;
at rates that are proportional to their weight, and these rates are
about 16'per sec^2, so what is the strength of gravity, if not a/2 =
16'/sec^2?

Don

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  #6  
Old 09-14-2005, 12:05 AM
Randy Poe
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Default g is the strength of gravity


Don1 wrote:

Define "rate".


Nope.


Well, as that is not the acceleration or any kind of
velocity, I can't figure out why anybody would call it
a "rate" of anything.

- Randy

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  #7  
Old 09-14-2005, 12:13 AM
Sam Wormley
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Default g is the strength of gravity

Randy Poe wrote:

It's pretty obvious that Shead tries to be stooopid on purpose.
A strategy of many a troll.
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  #8  
Old 09-14-2005, 12:47 AM
Don1
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Default g is the strength of gravity

Randy Poe wrote:
According to Webster: Rate is a quantity, amount, or degree of
something measured per unit of something else.


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  #9  
Old 09-14-2005, 12:47 AM
Don1
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Default g is the strength of gravity

Randy Poe wrote:
According to Webster: Rate is a quantity, amount, or degree of
something measured per unit of something else.


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  #10  
Old 09-14-2005, 12:50 AM
Randy Poe
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Default g is the strength of gravity


Don1 wrote:

Now tell me how this definition of "rate" applies to g/2.

- Randy

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