## Homework 3, due February 4, 2008.

Due Wednesday, February 4, 2008.
goodwine
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### Homework 3, due February 4, 2008.

From the course text: 6.1 (if you have not already done it), 6.9-6.12, 7.4 and 7.5. If you did do 6.1 on homework 2, you don't have to do it again, but indicate that you did so that it is easy for the graders to keep track of it.
Bill Goodwine, 376 Fitzpatrick
sjensen1

### Re: Homework 3, due February 4, 2008.

Problem 6.8 was assigned last week. Should we still work through it?
goodwine
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### Re: Homework 3, due February 4, 2008.

sjensen1 wrote:Problem 6.8 was assigned last week. Should we still work through it?
Sorry, that was a mistake. I edited the assignment to remove it.
Bill Goodwine, 376 Fitzpatrick
Anon

### Re: Homework 3, due February 4, 2008.

Professor,

If we did problem 6.1 in assignment #2, but applied the incorrect method to solve for the solution may we re-do it to obtain full credit as opposed to the credit that might have been lost by doing it in assignment #2?
wgarraha

### Re: Homework 3, due February 4, 2008.

Should we assume any kind of units for problem 7.4 or should we leave b, k, and m as variables?
AlexDarr

### Re: Homework 3, due February 4, 2008.

1) For irrational numbers (1+/- sqrt(15)), two of the eigenvalues of the matrix, is there a relationship between their eigenvectors, like there is with complex numbers?

2) Evaluating (A-lamda*I) where lamda is 1+/- sqrt(15), I got eigenvectors of [0;0;0;0] for both. I checked my math for both, and it seems right. Are two trivial eigenvectors acceptable, since the other eigenvalues yield nontrivial eigenvectors?
AlexDarr

### Re: Homework 3, due February 4, 2008.

Scratch that last post
satkinso

### Re: Homework 3, due February 4, 2008.

wgarraha wrote:Should we assume any kind of units for problem 7.4 or should we leave b, k, and m as variables?
I'm actually wondering myself if, when it says, "Determine the equations of motion," it means to just find the differential equations?
goodwine
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### Re: Homework 3, due February 4, 2008.

satkinso wrote:
wgarraha wrote:Should we assume any kind of units for problem 7.4 or should we leave b, k, and m as variables?
I'm actually wondering myself if, when it says, "Determine the equations of motion," it means to just find the differential equations?
Yes the equations of motion are the differential equations. Unless it says to solve them, you don't have to do so.
Bill Goodwine, 376 Fitzpatrick
gtorrisi

### Re: Homework 3, due February 4, 2008.

for problem 7.5 when it says to write a computer program to determine an approximate numerical solution for the system, do you mean you want us to show a graph of the motion vs. time, and if so, do we need to show each mass or just the first one, or is it asking for something else?
goodwine
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### Re: Homework 3, due February 4, 2008.

gtorrisi wrote:for problem 7.5 when it says to write a computer program to determine an approximate numerical solution for the system, do you mean you want us to show a graph of the motion vs. time, and if so, do we need to show each mass or just the first one, or is it asking for something else?
It's intentionally open-ended. Submit something that clearly communicates the nature of how the masses are moving. It's up to you to determine what you think is best.
Bill Goodwine, 376 Fitzpatrick
goodwine
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### Re: Homework 3, due February 4, 2008.

Anon wrote:If we did problem 6.1 in assignment #2, but applied the incorrect method to solve for the solution may we re-do it to obtain full credit as opposed to the credit that might have been lost by doing it in assignment #2?
You can re-do it, but put a note on your homework saying that you want this one to count and not the previous one.
Bill Goodwine, 376 Fitzpatrick
goodwine
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### Re: Homework 3, due February 4, 2008.

I had a few questions on problem 7.5: How do you fit the f(t)
equation into the xsidot = a*xsi? Is it just an added on thing after
that? Secondly, in the computer program is it possible to input
everything as an array or do you need to do x1dot(1) = x1(2),
x1dot(2) = etc..? Thanks
For the first question, it is an extra term since it does not depend on any of the components of xi.

For the second question, it depends on the programming language you use, but the answer is probably that you have to input everything term by term.
Bill Goodwine, 376 Fitzpatrick
goodwine