Index of Refraction

Honors Physics conducted an investigation of torque and rotational equilibrium. It was a wild and wooly experience, such that I made sure that the laptops were safely removed from the lab benches prior to the lab period. When we think about balance, we are thinking about torque and rotational equilibrium. Those amazing mobiles that people construct are based on these principles. Keep the net torque on the system at zero and there will be no rotation. Masses are carefully placed to generate equal positive and negative torque. We also have to consider linear equilibrium, though. The pieces can’t snap the strings! The second part of the lab had you pull both equilibria together in what looked like a physics version of Twister. However, with effort, rotational and translational equilibrium was attained and the meter sticks finally behaved themselves. We’ll discuss the lab tomorrow and look more deeply into the idea of torque. Here’s a couple of preview videos if you just can’t wait:





Physical Science B went over their lab investigations and discussed their lab data in light of our work with machines. Maximize the separation between the input and output distances and you maximize the mechanical advantage of the machine. Also, don’t expect efficiency to be great – that is one of the tragic costs of using machines. It costs you more work to do the job with a machine than if you had simply done it yourself. Then, we turned our attention to energy and examined gravitational potential and kinetic energies. Is energy stored or is it actively fueling work? Regardless, it is still energy, measured in Joules. The practice worksheet will allow you to work with the GPE and KE formulas and we will go over them on Monday. The answer key is online and can be accessed THROUGH THIS LINK.

Physical Science E went over their kinetic energy homework and, after a review of GPE and KE, worked on a problem set for both energy types. The answer key is online (see the link above) and we’ll go over the work tomorrow in class. Also, as promised, here are a couple of energy videos:





Physics F and G discussed gravity and factors that affect the magnitude of the force of gravity between objects. Mass and distance are the players , with distance having more of an impact than mass. That pesky r²…double the mass, you only double for the force. Double the distance and the gravitational attraction drops to 1/4 the original value. Remember when working problems that when you solve for distance, makes sure that you are solving for distance and not distance-squared. Too often, folks forget to take that final square-root and end up with the wrong answer. Remember that we are looking at next Tuesday as your assessment day. That gives us a couple of review days between now and then, so prepare any questions you have to address in class.
Homework:

Honors Physics A: Complete lab write up
Physical Science B and E: Complete energy problems worksheet.
Physics F and G: Practice 7I #1,2 and Chapter Review items #31, 35, 39, 50