Reading Quiz 19 Key

Due 3:30 pm, Tuesday, November 3rd

Physics 105, Fall Term, 2009


Reading: Chapter 9.1-9.3

Did you complete the reading assignment?

Yes
No

KEY CONCEPTS:

1) Solids maintain form and shape unless they are stressed.

2) Density depends on both the mass and volume of an object.

3) Pressure is the force applied to a specific area.

Because most of you are familiar with and understand density and pressure in solids, we will skip over them in the reading quiz. Young's Modulus is a less well known characteristic of solids. You have actually been exposed to it earlier in this class through Hooke's law and elastic spring potential; they are just specific applications of Young's Modulus.

We generally think of solids as matter that maintains its shape and form; however, some solids can lose there form a lot more easily that others. Young's Modulus basically refers to the deformability of a solid, but not the breakability of the solid. To understand how these concepts are different from each other, go to: http://schools.matter.org.uk/Content/YoungModulus/stiffnessExercise.html and complete the stiffness and strength chart. Note that this is a site from the UK so biscuit does not have the same definition we use in America, but instead means any small, hard, grain based product, like a cookie, dehydrated block of wheat, or cracker, but not a dinner roll.

What has a higher Young's Modulus, a cracker or a nylon rope?

Cracker
Nylon rope

One way to really understand what Young's Modulus actually is, is by performing the lab on this website.  To perform the experiment, press the 'Next' button under the title of the page and follow the instructions on the website. Notice though that the website refers to Young's Modulus with an E instead of a Y.

Is Young's Modulus for a solid dependent upon the geometrical features (like length and width) of a solid?

Yes
No

In the online lab, you should have found Young's Modulus for steel to be about 2.1 x1011 N/m2. How much force needs to be applied to stretch a steel wire that is 1 mm thick?


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Was there anything that you didn't understand in the reading assignment?  What was confusing to you?


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