Circuit practice

Blinky!

HW

Sorry for delay -please solve this circuit

Intro electronics manual

Located at:

goo.gl/l5Mzpi

HW, and intro to bridge designer

Read chapter 12 - or at least start reading it.

Bridge Design – Using West Point Bridge Designer

Now that you have at least a little understanding of how trusses work, it’s time to play around with some bridge building. The United States Military Academy—hereafter referred to as West Point—has been running a Bridge Design contest for high school and middle school students for more than 10 years. Students design a bridge that must satisfy certain specifications, while minimizing the overall cost. Cost is, of course, a real-world concern since materials and labor cost money. While we will not be entering the West Point contest, we can use the software to play around with bridge design and learn, we hope, some more about some basic engineering principles.

The link below is to the website where you can find the bridge design software. After you go to the website, you should see in the middle of the screen a link to the download area. Once you get to the downloads area, read carefully so that you’ll pick the correct link for downloading (basically, you need to know whether your Macintosh computer has Apple Java). After you install the software come back to this document.

http://bridgecontest.org

There’s a 26-minute video tutorial that you can view at the bridge contest website. You can find it under the “Resources” tab at the top. After going through this video, you’ll need to learn one more thing about the program, so open up the program and load up the sample design for the continuous arch. Select one of the members—remember that a “member” is a bar or cable. On the right side of the screen you should see the member you selected highlighted in blue. At the top of that window where the member has been highlighted is the tab “Member Details”. Click on this tab. You should now be seeing more detail about this particular member, including information regarding the member’s material properties, dimensions, and cost.

1.     As a check of your understanding, find the member numbered 10 and write down its mass density, moment of inertia, and member cost.

2.     Start up a new bridge design in the program.  Try to design a bridge that doesn’t look exactly like one of the pre-loaded designs. Make sure to test it out so that it will pass the load test. Lastly, print out a copy of your design.

Project to start next week:

Now, build a truss-style bridge, either based on this design or an entirely different one.  You will use basswood and gusset “plates” made from manila folder material.  We will test it to failure using a method described in class.

HW

Solve for the practical lab problems completed in class - do the "left torques" equal the "right torques"?  Don't forget about the mass of the meter stick.

Reconsider the scaffold problem.  You have a 4-m long scaffold (60 kg), supported by cables at the extreme ends.  Two workers are standing on it:  Jack (75 kg, 1-m from the left) and Jill (65 kg, 2.5-m from the left).  What is the tension in each cable?

Have a look at the ladder problem in the student guide.  Note that there is an error in the text.  Under rotational equilibrium, it should actually say:

Rotational equilibrium:

W (L/2 cos q) = F (L sin q)

Note the change from L to L/2 --- this is because the weight of the ladder acts through its center of gravity.

Try to make sense of the ladder problem and solve the one in the homework if you can.  I'll post a solution before class meets again.