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☖ Forums → Discussion Forum → Newton's Law of Gravitation
Newton's Law of Gravitation
2005-11-25, 10:27 AM #1
In Figure 13-34, a square of edge length 22.0 cm is formed by four spheres of masses m1 = 7.00 g, m2 = 3.50 g, m3 = 1.50 g, and m4 = 7.00 g. In unit-vector notation, what is the net gravitational force from them on a central sphere with mass m5 = 2.30 g?

[http://www.webassign.net/hrw/hrw7_13-34.gif]

Okay this is what I did so far.
Since m4 and m1 are equal, they can be neglected. This leaves....

F = Gm5(m2-m3) / r^2

I then tried to multiply it by cos 45 degrees to get the i component and sin 45 degrees to get the y component, but this isn't working. Why is that?
2005-11-25, 10:28 AM #2
huh?

look at the purty dots...
If you choose not to decide, you still have made a choice.

Lassev: I guess there was something captivating in savagery, because I liked it.
2005-11-25, 10:35 AM #3
You forgot got the densitogram digit divider.
Ok so I lied, I don't know wtf yer missing. There is no such thing as a densitoblblabla
Was cheated out of lions by happydud
Was cheated out of marriage by sugarless
2005-11-25, 11:46 AM #4
I got

8.97e-13 (i + j)

You didnt say what you used for an r value, but i used 11 root 2.

Then did it the same as what you had.
2005-11-25, 11:56 AM #5
Originally posted by Cloud:
...Why is that?

You could always, well...you know.....ask your teacher.... ;)
And when the moment is right, I'm gonna fly a kite.
2005-11-25, 12:09 PM #6
Im sure his teacher has off til monday.

Same reason I'm at home studying in front of the distraction box.
2005-11-25, 12:13 PM #7
Fg m1 = [G(2.5)(3.5)/r^2]
Fg m2 = [G(2.5)(1.5)/r^2]

Fg net = Fg m1 - Fg m2 ~=1.378 x 10^-12 N at an 45 degrees N of x axis

I don't think you should be combining m3 and m2 because they're separate masses.
I could be wrong, though. I was bad at this unit, and I can't remember if there was a proper process to doing this. I just found each individual force vector n combined them.
一个大西瓜
2005-11-25, 12:22 PM #8
@_@
Was cheated out of lions by happydud
Was cheated out of marriage by sugarless
2005-11-25, 4:10 PM #9
I forgot to mention, do not add the i and j components. Leave them as separate answers.


Quote:
You could always, well...you know.....ask your teacher....

Seems like I will never hear the end of this....asking my teacher won't be any help because I have a hard time understanding him through his accent.
2005-11-26, 4:24 AM #10
I'll have a gander if I get a spare half hour today - if you're ever really stuck you can email me on martynpie at the mail of g :)
2005-11-26, 9:00 AM #11
Wow if massassi was a school id probably get straight A's!
[I.E Holy crap you'r smart pommy]
2005-11-26, 11:42 AM #12
If i was to do it I'd do it exactly like pommy.

there is no need to convert the forces into cos and sin components as they are in opposite directions to one another.
People of our generation should not be subjected to mornings.

Rbots
2005-11-26, 1:50 PM #13
Your views of gravity and time are flawed. Gravity as we know it doesn't really exist. Traditional physics says that objects are mutually attracted to each other. Myself and a senial professor at my college have come up with a new theory, gravital physics. You see, all objects are just constantly expanding, so they appear to move together, but infact, they don't. Once you can let go of the existence of time and gravity, you may become enlightened as I have.
Bassoon, n. A brazen instrument into which a fool blows out his brains.
2005-11-26, 2:20 PM #14
Originally posted by Emon:
Your views of gravity and time are flawed. Gravity as we know it doesn't really exist. Traditional physics says that objects are mutually attracted to each other. Myself and a senial professor at my college have come up with a new theory, gravital physics. You see, all objects are just constantly expanding, so they appear to move together, but infact, they don't. Once you can let go of the existence of time and gravity, you may become enlightened as I have.

That would imply that more voluminous objects would have more gravity, rather than more massive ones. And singularities would serve as antigravity devices.

Edit: That would mean a ton of feathers would weigh more than a ton of bricks.
2005-11-26, 2:30 PM #15
Originally posted by Jon`C:
That would imply that more voluminous objects would have more gravity, rather than more massive ones. And singularities would serve as antigravity devices.

Edit: That would mean a ton of feathers would weigh more than a ton of bricks.

You're stuck on the primitive, scalar concepts of "mass" and "weight." In reality, they don't exist either.
Bassoon, n. A brazen instrument into which a fool blows out his brains.
2005-11-26, 2:42 PM #16
Your world is a nightmarish place of magic and dragons.
2005-11-26, 4:54 PM #17
it is also a comedy place in which I have have frolicked (and berated idots) ;)
2005-11-26, 5:47 PM #18
So did you ever figure this problem out cloud?

Originally posted by Cloud:
I forgot to mention, do not add the i and j components. Leave them as separate answers.


I added them to simplify, because the two components are are going to be the same, whatever the answer ends up being.

[QUOTE=James Bond]there is no need to convert the forces into cos and sin components as they are in opposite directions to one another.[/QUOTE]

The problem asks for unit vector notation.
2005-11-26, 5:50 PM #19
:D I have no idea what any of you are talking about, so I'll just continue to smile :D
I had a blog. It sucked.
2005-11-27, 5:08 PM #20
Originally posted by Warehouse:
So did you ever figure this problem out cloud?



I added them to simplify, because the two components are are going to be the same, whatever the answer ends up being.



The problem asks for unit vector notation.



No I haven't. I only get one more submission that's why I'm wary. Are you sure both of the components are the same in value? As I have said there are two spaces:
_______N i + ________N j
2005-11-27, 5:32 PM #21
All I know is that when you throw something up, there's a good chance it will come back down.
2005-11-28, 5:56 PM #22
Okay I tried using Pommy's method with the numbers my friend's has and it yield him the wrong answer.
2005-11-28, 7:46 PM #23
Originally posted by Reid:
All I know is that when you throw something up, there's a good chance it will come back down.

.
Attachment: 8903/puke.gif (4,880 bytes)
"Harriet, sweet Harriet - hard-hearted harbinger of haggis."
2005-11-29, 4:07 AM #24
Originally posted by Warehouse:
The problem asks for unit vector notation.
Kinda missed that part :)....either way I they would have been equal on each vector as the force was acting at 45 degrees to the x-axis as pommy mentioned.

if your not getting the right numbers...well, I'm stumped.
People of our generation should not be subjected to mornings.

Rbots
2005-11-30, 6:19 PM #25
Guess I have to try a physics forum....

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