Question Quick Physics question

[Bj]

Edit: As you can tell, I am not having a good day... this will be back to readable in a quick few seconds...


Ok guys so a little physics question about Gravitational constant and law of universal gravitation.

So..

(I am trying to find the force of the Sun on my body)

Everything alright so far? Good, so I have the answer, but this is where I get confused,

Google defines G as:

So when I enter the entire equation into Google (to do the math for me...)

which was:

(G *60* mass of earth)/ AU^2

It keeps the m^3.... stuff.

I look in my book it plugs in the equation like...

which makes the answer to my question ~1.06364267 milligrams, but why would the book remove the units? Does it not matter anyway or whats the deal?

 

[Izack]

You result should be in Nm/kg^2. (Newton-metres per kilogram squared.)

EDIT: What am I talking about?? My answer makes no sense!

 

[Notebook]

I can't see Bj's formula, just little boxes with red "x"'s. I presume a browser setting? Any advice please?

N.

 

[jedidia]

(G *60* mass of earth)/ AU^2

The Gravitational Constant itself has a unit, which goes like this:

m^3kg^-1s^-2

As you can see, meters apear in that unit, so you CAN'T just change your input to AU's. You have to convert it into meters, or you have to convert the gravitational constant to AU^3kg^-1s^-2 (I would recommend the former).

 

[Bj]

The Gravitational Constant itself has a unit, which goes like this:

m^3kg^-1s^-2

As you can see, meters apear in that unit, so you CAN'T just change your input to AU's. You have to convert it into meters, or you have to convert the gravitational constant to AU^3kg^-1s^-2 (I would recommend the former).

I thought Google would automatically do that for some reason, OK

well then

(6.67300 × 10^-11 *60* 5.9742 × 10^24)/ 149598000^2

um wait, what? Answer:

1.06881012.. kg? (that's the units I used for my weight, and Suns weight)

Suns gravity effects my body that much?



Oh wait I goofed, I used the mass of Earth instead of the sun;

(6.67300 × 10^-11 *60* 1.98892 × 10^30)/ 149598000^2

355 826.358?

That answer has got to be in milligrams. That would make more sense, but still, that's a pretty big difference in weight I would think...

 

[SiberianTiger]

355 826.358?

That answer has got to be in milligrams. That would make more sense, but still, that's a pretty big difference in weight I would think...

That's in kilograms, and this is how much you would weight if the Earth stopped and got fixed at its position relative to the Sun. Given that happened around midnight, and you've also got to add your weight on Earth in kilograms... Guess what happens at other times of day!

 

[Bj]

That's in kilograms, and this is how much you would weight if the Earth stopped and got fixed at its position relative to the Sun. Given that happened around midnight, and you've also got to add your weight on Earth in kilograms... Guess what happens at other times of day!

Wait I goofed again,

Radius needs to be expressed in meters not km.

(6.67300 × 10^-11 *60* 1.98892 × 10^30)/ 149598000000^2

oh and the result turns to force (newtons)

Which in this case is:

0.355826358 n

or 0.0362718 kg

or 1.27945009 ounces

OK THAT makes sense. :lol:

only thing that doesn't is removing the Nm^2/kg^2 but ours is not to question why



(I had the pictures of the latex, but they disappeared again...

 

[RisingFury]

F = G*m*M / r^2

m = 60 kg
M = 2*10^30 kg
G = 6.67 * 10^-11
r = 15 * 10^10 m

Which gives ~0.35 N.

Use www.wolframalpha.com next time. It'll let you get away with input as sloppy as
G*60*2*10^30/AU^2

 

[tblaxland]

(I had the pictures of the latex, but they disappeared again...

Your

 

[SiberianTiger]

0.355826358 n

or 0.0362718 kg

or 1.27945009 ounces

OK THAT makes sense. :lol:

Damn, I wanted it to be more! :lol: