Tuesday, January 25, 2011

MA 1-25

Today in class, on 1/25/11, we did many things.

First, we did a practice problem for density: a soup can, with radius=2cm, h=5cm, and the mass=300g. We had to find the density. In order to, Finley gave us a cool pneumonic device to help us rememebr formulas for circles and cylinders: for a circle, it's 3.14r(squared), and since a cylinder is really a bunch of circles on top of each other, you multiply that equation by the height, h. You get 3.14r(squared)h. The density was 4.78 grams per cm.3

We also went over the homework. It would be hard to put up all the answers here, but i'll put some of the conclusion questions:

2. An object with a density of 0.67 kg/L would float 2/3 underwater.

3. A floating object has an upward force that is equal to the downward weight.

4. What would happen to an ice cube if it was dropped into a glass of 100% ethanol (density= 0.789 kg/L)? Would it be pushed up more or less? Why do you think this?

It would be pushed up more and down less. It would be because, if you look at the data, you can find this rule: if the object is less dense than the liquid, it floats. Contrariwise, if it is denser than the liquid, it will sink more.

http://en.wikipedia.org/wiki/Density
that helped me understand some of it.
-MA
3rd