# Why is the gravitational potential against distance graph a curve? Watch

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The equation is V =-GM/r so wouldn't this mean that the relationship is V ∝ 1/r which is a straight line not a curve.

Also, I need an explanation for this question:

Which one of the following graphs correctly shows the relationship between the gravitational force,

The answer is D but I don't understand why C can't be the answer as well. All help is appreciated thanks!

Also, I need an explanation for this question:

Which one of the following graphs correctly shows the relationship between the gravitational force,

*F*, between two masses and their separation*r*.The answer is D but I don't understand why C can't be the answer as well. All help is appreciated thanks!

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#2

F=GMm/(r^2)

Rewriting this a little u get

F=GMm*(1/r^2)

Comparing this to y=mx c u get he gradient as GMm, the intercept is the origin and the x axis must be 1/r^2.

For a graph as in c, consider

R^2=0.5, F=2GMm

R^2=1, F=GMm

R^2=2, F=GMm/2

As r^2 approaches zero F approaches infinity therefore the graph is not linear. In other words for a double in r^2, F halves.

Try plotting the above values on a graph and u should see it is non linear.

For ur first question u will get a straight line graph, try rearranging for urself as i have done above and comparing to equation of straight line.

Rewriting this a little u get

F=GMm*(1/r^2)

Comparing this to y=mx c u get he gradient as GMm, the intercept is the origin and the x axis must be 1/r^2.

For a graph as in c, consider

R^2=0.5, F=2GMm

R^2=1, F=GMm

R^2=2, F=GMm/2

As r^2 approaches zero F approaches infinity therefore the graph is not linear. In other words for a double in r^2, F halves.

Try plotting the above values on a graph and u should see it is non linear.

For ur first question u will get a straight line graph, try rearranging for urself as i have done above and comparing to equation of straight line.

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(Original post by

F=GMm/(r^2)

Rewriting this a little u get

F=GMm*(1/r^2)

Comparing this to y=mx c u get he gradient as GMm, the intercept is the origin and the x axis must be 1/r^2.

For a graph as in c, consider

R^2=0.5, F=2GMm

R^2=1, F=GMm

R^2=2, F=GMm/2

As r^2 approaches zero F approaches infinity therefore the graph is not linear. In other words for a double in r^2, F halves.

Try plotting the above values on a graph and u should see it is non linear.

For ur first question u will get a straight line graph, try rearranging for urself as i have done above and comparing to equation of straight line.

**Shaanv**)F=GMm/(r^2)

Rewriting this a little u get

F=GMm*(1/r^2)

Comparing this to y=mx c u get he gradient as GMm, the intercept is the origin and the x axis must be 1/r^2.

For a graph as in c, consider

R^2=0.5, F=2GMm

R^2=1, F=GMm

R^2=2, F=GMm/2

As r^2 approaches zero F approaches infinity therefore the graph is not linear. In other words for a double in r^2, F halves.

Try plotting the above values on a graph and u should see it is non linear.

For ur first question u will get a straight line graph, try rearranging for urself as i have done above and comparing to equation of straight line.

Also, do you know the answer about the gravitational potential?

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(Original post by

The equation is V =-GM/r so wouldn't this mean that the relationship is V ∝ 1/r which is a straight line not a curve.

Also, I need an explanation for this question:

Which one of the following graphs correctly shows the relationship between the gravitational force,

The answer is D but I don't understand why C can't be the answer as well. All help is appreciated thanks!

**AspiringUnderdog**)The equation is V =-GM/r so wouldn't this mean that the relationship is V ∝ 1/r which is a straight line not a curve.

Also, I need an explanation for this question:

Which one of the following graphs correctly shows the relationship between the gravitational force,

*F*, between two masses and their separation*r*.The answer is D but I don't understand why C can't be the answer as well. All help is appreciated thanks!

you wrote v a 1/r so v=k/r k is -GM

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(Original post by

Consider a graph of y=1/x let v=y and x=r and then -G and M are transformations

you wrote v a 1/r so v=k/r k is -GM

**bruh2132**)Consider a graph of y=1/x let v=y and x=r and then -G and M are transformations

you wrote v a 1/r so v=k/r k is -GM

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#6

(Original post by

I honestly don't understand what you mean. Sorry

**AspiringUnderdog**)I honestly don't understand what you mean. Sorry

Also At GCSE Maths you might have learned that if something is proportional to something else you can write an = if you add a k

i.e x ppt y so x=ky

or x ppt 1/y so x=k/y

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(Original post by

Do you do A level maths/ do you know what the graph of 1/x is?

Also At GCSE Maths you might have learned that if something is proportional to something else you can write an = if you add a k

i.e x ppt y so x=ky

or x ppt 1/y so x=k/y

**bruh2132**)Do you do A level maths/ do you know what the graph of 1/x is?

Also At GCSE Maths you might have learned that if something is proportional to something else you can write an = if you add a k

i.e x ppt y so x=ky

or x ppt 1/y so x=k/y

So for the graph question. F against r^2 should be a curve so it is incorrect.

Thanks!

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#8

(Original post by

Okay actually I do get what you mean. Having a graph of V against r and plotting V=1/r would be a curve. Holy crap lol I can't believe that I missed this.

So for the graph question. F against r^2 should be a curve so it is incorrect.

Thanks!

**AspiringUnderdog**)Okay actually I do get what you mean. Having a graph of V against r and plotting V=1/r would be a curve. Holy crap lol I can't believe that I missed this.

So for the graph question. F against r^2 should be a curve so it is incorrect.

Thanks!

f ppt 1/r^2 so if you let 1/r^2 be let's say y

you have f ppt y which would be a straight line if you plot f against y which is f against 1/r^2 if you get what I'm saying

basically f ppt 1/r^2 so there should be a straight line through the origin.

Normally you should consider y=mx+c to see if the graph passes through the origin but here c=0.

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#9

Because you cannot tell if the graph would go through the origin if it was swapped to 1/r^2

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