# Help with Project!

Discussion in 'Odds & Ends' started by USCfan, Mar 4, 2005.

1. ### USCfanProfessional

Joined:
Dec 29, 2004
Messages:
815
Is anyone familiar with vectors?

Here's my problem: I have a position vector r, and the 2nd derivative = [-GM/(abs.value of r)cubed] x r.

According to my textbook, this means the second derivative is a scalar multiple of r, and therefore:

the 2nd derivative of r x r = 0

Can anyone explain this to me? Is it some rule dealing with vectors?
This is really urgent... I would appreciate any help. I could email you a copy of my prject, if you don't understand what I am trying to say.

2. ### battousai555Rookie

Joined:
Dec 5, 2004
Messages:
107
Well, if you use the law of sine, cosine, and tangent all at once and multiply by the square root of a piece of pie divided by the atomic mass of adamantium this should give you whatever you asked.

3. ### fretstainNew User

Joined:
Feb 27, 2005
Messages:
18
could you email it to me? the_damn_echeverria@gmail.com? I haven't done this type of thing in a while but I'd like to see if I can make sense of it anyway

4. ### USCfanProfessional

Joined:
Dec 29, 2004
Messages:
815
fretstain,
I emailed you.

5. ### Power GameProfessional

Joined:
Jun 30, 2004
Messages:
1,151
I think I can do this... I'll talk to you later

6. ### fretstainNew User

Joined:
Feb 27, 2005
Messages:
18
for some reason it seems that my email address isn't working... could you give a better description here?

7. ### Bigmal87Guest

who'd have thought so many maths geniuses all in one thread