# Trying to figure out gravitational attraction between two objects.

#### LuigiHomer

Trying to figure out the gravitational attraction between two objects using Newton's Law of Universal Gravity.Need to figure out what the force is.Here is a model.If anything is in ordinary parentheses then it is an exponent.

----------------------G
--------____________|_____________400x300
F1=F2=[6.673x10(-11)N m(2) kg (-2)] -----
-------------------------------------2,000(2)

Force is proportional to the product of the two masses{120,000}and inversely proportional to square of distance between two point masses.{4,000,000}

Please help me figure out what F1 is,since F1 is equal to F2.

-LH

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#### DaveC426913

Gold Member
First thing you must do is ensure all your numbers are in the right units: kilograms & metres (since those are the units that G is in). I don't know what units your numnber are in now.

F - the force between them - will be equal to your formula there.

#### LuigiHomer

Okay.The two point masses are in KG.The distance is in metres.G is in Newtons.

#### DaveC426913

Gold Member
So, what answer did you get?

The formula you have listed will calculate "the force of attraction between two bodies". One force, not two. Not sure where the F1=F2= came from.

#### LuigiHomer

I can't figure it out.Kind of new to the concept of using Newton's laws.Kind of new to physics.

#### molinaro

I would think F1 is force felt by object #1 and F2 is the force felt by object #2, and they are equal in magnitude, while opposite in direction.

Simply multiply and divide and you are done.

G x M1 X M2 / (R x R) = F1 = F2

From your post we have:

M1 = 400 KG
M2 = 300 KG
R = 2000 M

And we know G.

So, just do the math! There's no physics left to figure out.

#### LuigiHomer

I don't have a calculator that can even REGISTER newtons,and our teacher took it away.:(What a meanie.

#### LuigiHomer

My sister THINKS it is 0.030.

#### LuigiHomer

Do you guys have a suggestion
for a good, reliable computer calculator for free that can do what Molinaro said to do?

#### LuigiHomer

@ DaveC,It is that they BOTH exert gravitational force.F1 is equal to F2,which is the other force.

#### molinaro

Do you guys have a suggestion
for a good, reliable computer calculator for free that can do what Molinaro said to do?
> START > PROGRAMS > ACCESSORIES > CALCULATOR

then menu > VIEW > SCIENTIFIC

#### LuigiHomer

My sister didn't incorporate G.My head hurts.I'm only in 5th grade,you know.

#### DaveC426913

Gold Member
I don't have a calculator that can even REGISTER newtons,and our teacher took it away.:(What a meanie.
You don't need a calculator that registers' Newtons...
You're just doing math.

#### DaveC426913

Gold Member
@ DaveC,It is that they BOTH exert gravitational force.F1 is equal to F2,which is the other force.
They do both exert a force. That formula will calculate the entire forfce between the two masses.

#### LuigiHomer

You don't need a calculator that registers' Newtons...
You're just doing math.
Once again,I AM A FIFTH GRADER!

#### DaveC426913

Gold Member
Once again,I AM A FIFTH GRADER!
I'm sorry, I missed that.

Have you learned exponents?
6.67x10^-11 is equal to .0000000000667

So:

F = (.0000000000667)*400*300 / (2000^2)

Masses of 300-400kg that a distance of 2km have an extremely small force of attraction.
Your answer should be a very, very small number - about 11 zeros.

#### jtbell

Mentor
I'm only in 5th grade,you know.
No, we didn't know that, until you mentioned it in this post. :uhh:

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