Welcome to the website of ME 274 for the Fall 2008 semester. On this site you can view blog posts, add your own blog posts and add comments to existing posts. In addition to the blog are links to course material: course information, information on solution videos, exams, quizzes, homeworks and other course-related material. Direct links to the homework solution videos are also available on the left side of this page.


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Dec 1, 2008

VIB 3

In VIB 3, I am not able to follow a certain step. We have the disk moment equation: -k(R*theta)*(R) + T*R = Io*omega_double dot. We then have from the sum of forces in Y for the block that T = m*g - m*y_double dot. combining the two, -k*R^2*theta + (mg - m*y_double dot)*R = 1/2*mR^2*theta_double dot. If you expand ..."(mg - m*y_double dot)*R" it would be "mgR - m*y_double dot*R" correct? Later, in the video solution, I can't find out what happened to the R in the mgR term. That would still carry through to the EOM and make it have an R^2 term on the left and an R term on the right, that could cancel. If you could clear that up for me, I would appreciate it.
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1 comment:

CMK said...

You are correct -- I unfortunately did not carry along the R on the weight term when I expanded it out. The RHS of the final form of the EOM should read be m*g*R (not m*g).

Fortunately, this does not affect the answer for the natural frequency, only the inhomogeneous term on the RHS of the EOM.

Apologies for the algebra error.

December 1, 2008 at 10:18 PM

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