3-17-09

Today was a demo day due to the pssa testing that the juniors had. Mr. Manning said that pages 11-13 are due tomorrow and we will check them when the juniors return. We got notes on rotational and torque notes (page 14). In class we did a lot of different demos. 1. There was a spinning wheel that we would stand on. We held weights and when we moved them closer to our body we rotated faster. When we moved them far away we slowed down again. The heavier the weight the faster you would go when the weight was near your body. Whenever the mass is very close to your body there is hardly any rotational inertia and we will spin faster. When objects are far away they will have more rotational inertia and will not want to spin. The same happened when students sat down on the wheel and pulled their legs in and out. 2. Another demo we did was with a bicycle wheel. When the wheel turned to the side it made the student spin in the direction of the torque. This is because of the conservation of momentum. The wheel produces a torque. A torque is a spinning action. If you hold the wheel in your hand you can experience the torque. It exerts a force from a distance away from the axis of rotation. 3. At the end of class we watched a video of Julius Sumner Miller and he showed us the difference between discs that have mass evenly distributed and discs that have nothing in them. We found that when the mass was distributed equally, the disc rolled faster. He showed us the proofs and mathematics behind this feat.

There was no homework today unless you didn't do pages 11-13.