3-10

Today was a club day so physics class was shortened.

Mr. Manning started class with a pretty sweet demonstration. He first swung a little board attached by many ropes around in a circle. He said that the board at the end of the rope wants to go in a straight line. This idea is supported by inertia, although inertia is not actually acting on it. But since the board wants to go in a straight line, Mr. Manning has to pull the rope (and therefore the board too) towards the center of the circle, causing the board to turn, and go around in a circle. Mr. Manning then proceeded to put a small cup of water on the board. He then swung it around in a circle, just like before. Not a single drop of water was spilled! He explained that friction holds the cup of water on the board. It was very beneficial to have water in the cup because the more water caused more weight and more weight caused more friction and more friction resulted more stability of the cup on the board. This was a demonstration of a centripetal force, and tension was vital in this demonstration. For a diagram of what this may have looked like click here. []

Then we worked on the “Centripetal Forces Lab: Swingin’ Nephews.”

Written on the board was: - All sets of data will produce curved lines on graph - Only 2/3 graphs will straighten when data is squared - Print 3 curved graphs and 2 straightened graphs

So we got the laptops and with Graphical Analysis worked on creating the graphs for our 3 sets of data. When you are trying to straighten the graphs, remember to only square one set of data at a time. For example- in the first set of data, try squaring Centripetal Force, and then if you want to try squaring Speed also then put the original Centripetal force back in the spreadsheet and square the Speed quantities. Same goes for Speed and Radius in the second set of data, and Centripetal Force and Radius in the third set of data. We will have more time to finish that in class tomorrow.

Mr. Manning announced that our unit test will not be until next Friday, 3/20/09. This is because there is PSSA testing next week. Hooray. We may start the next unit before that test.