Homework 6, due October 10, 2016.

Due at the beginning of class on MONDAY, October 10, 2016. No extensions.
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goodwine
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Homework 6, due October 10, 2016.

Post by goodwine »

Reading: Chapter 4.

Exercises: 4.14, 4.17, 4.19 and 4.29.

For 4.14, also indicate how the solution would change if
  • the rotational speed of the rollers is increased
  • the coefficient of friction is increased
  • the density of the board is increased and
  • the length of the board is increased.
Bill Goodwine, 376 Fitzpatrick
garrett_schwartz

Re: Homework 6, due October 10, 2016.

Post by garrett_schwartz »

For problem 4.19 part 4, should we assume the initial value of b, or a decreased value?
goodwine
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Re: Homework 6, due October 10, 2016.

Post by goodwine »

garrett_schwartz wrote:For problem 4.19 part 4, should we assume the initial value of b, or a decreased value?
Use the initial value of b.
Bill Goodwine, 376 Fitzpatrick
kgilhoo1

Re: Homework 6, due October 10, 2016.

Post by kgilhoo1 »

For 4.19:
to solve for wn I did sqrt(k) and got 94.87
-> for zeta I did b/2*wn... this leaves me with z=12.65
I'm not sure how to correlate this z to the Fig 4.20 because the highest z value is 1. I may have just completely solved for z incorrectly
goodwine
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Re: Homework 6, due October 10, 2016.

Post by goodwine »

kgilhoo1 wrote:For 4.19:
to solve for wn I did sqrt(k) and got 94.87
-> for zeta I did b/2*wn... this leaves me with z=12.65
I'm not sure how to correlate this z to the Fig 4.20 because the highest z value is 1. I may have just completely solved for z incorrectly
The natural frequency is sqrt(k/m) so should be 3. With that your zeta should be in the right range.
Bill Goodwine, 376 Fitzpatrick
kgilhoo1

Re: Homework 6, due October 10, 2016.

Post by kgilhoo1 »

Thank you!
ccunnin6

Re: Homework 6, due October 10, 2016.

Post by ccunnin6 »

For question 4.29, is the equation x'' + 1/(5x') +... or x'' + (1/5)x' +...?
goodwine
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Re: Homework 6, due October 10, 2016.

Post by goodwine »

ccunnin6 wrote:For question 4.29, is the equation x'' + 1/(5x') +... or x'' + (1/5)x' +...?
The latter. The former would be nonlinear and also would not make any sense for vibrations.
Bill Goodwine, 376 Fitzpatrick
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