Showing posts with label Exam 3. Show all posts
Showing posts with label Exam 3. Show all posts
Dec 8, 2008
Dec 4, 2008
About the Exam 3 Solution
Professor, I noticed on the solution for the first problem on the exam that there was no force due to gravity shown acting on the bar in the Free Body Diagram. Is there supposed to be? I am unclear as to why there wouldn't be one somewhere on there. The way it's shown, it looks like the only force acting in the y direction is the Normal force at A pushing the bar upward, which I assume would imply that it's being lifted off the ground.
Dec 2, 2008
Lecture Example P. 75
For the problem on page 75 in our lecture notes, what is the numerical value for delta s that is used when computing the work for the system? I think its either the ten inches the drum drops or its the amount of cord that gets wrapped around the drum as it drops. Thanks
Dec 1, 2008
Exam No. 3 - last minute hint
During the help session this evening, I shared a hint related to Exam No. 3 with those present. I would like to share this with the whole class.
The grading of this exam will focus on setting up the problem (FBD, kinetics equations and kinematics). The algebra in solving will not be heavily weighted.
- For Problems 1 and 2, Steps 1-3 will be weighted at 18/20 points. The algebra and arithmetic in solving for the final answer will be weighted at 2/20 points.
- For Problem 3 (vibrations), Steps 1-4 (FBD, Newton, kinematics and EOM) will be weighted at 18/20. Since natural frequency is simple algebra from the EOM, this part will be weighted at 2/20 points.
In order to receive the full 18 points for setting up the problem, you will need to include ALL work. Only algebra/arithmetic should remain to be done in order to receive the 18 points.
Please use this hint in preparing for the exam.
If you have any questions on this, please ask me.
Soln Video 6/8
Why cant you sum the moments about A and set that equal to I(about A) times alpha? That was my first instinct when solving this problem. It is moving but not relative to the bar, which is our FBD. Do we need to look at the whole system when solving the moment equation instead of our FBD?? I think Im a little confused.
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.
Nov 24, 2008
Exam No. 3 - Common Access Point for Videos
Feel free to use the following links to get to the video solutions in preparation for the exam. Or, just use the usual links. If you want to download the videos onto your computer and do not know how, just leave a comment.
Sample Exam Solutions: Use scrollbar to locate video; click on image to view video.
Homework Solutions: Use scrollbar to locate video; click on image to view video.
Solution Video Modules: Use mouse to turn pages; click on image to view video.
Exam No. 3 details
Exam No. 3 is scheduled for 6:30-7:30 PM on Tuesday, December 2 in SMTH 108 (same room as for Exams 1 and 2). You can start 10 minutes earlier (at 6:20) if you want extra time for the exam.
The exam will cover Lectures 26-37. There will be three full-length questions (no multiple choice or short calculations questions on this exam) on:
- Newton-Euler equations
- Work-energy or impulse-momentum equations
- Vibrations: EOM and natural frequency
Sample exam questions 28-37 are related to the material covered on this exam. Video solutions for these sample exam questions are provided through the links on the left side of the blog. Each video solution is presented on a blog page on which you can directly view and/or add comments. Please use this to provide assistance to and receive assistance from others in the course.
A review video is provided to assist you in your studying for this exam. Click here for a copy of the equation page for Exam No. 3.
A help session is scheduled for 7PM on Monday, December 1 in Room ME 161. This review session will be run a little differently than for the earlier exams. For this help session, you are asked to work through the sample exam questions on your own prior to the help session. Use the solution videos provided to guide you with problems on which you have difficulty. During the help session, I will try to assist you with problems that you are having in general and/or with concepts that might not be clear in the solution videos for the sample exam questions.
Let me know if you have any questions related to Exam No. 3.
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