To Every Thing

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Honors Physics got to have a little fun today after going over their angular momentum and conservation of energy problems. For those problems, streamline your technique by remembering that combined objects in rotational motion (like a bike wheel and reflector) will have the same angular speed, regardless of position and that mass is not a necessary piece of information for the conservation of energy problems, if you are solving for height or velocity. Once we tidied up these problems, students had the opportunity to experience conservation of angular momentum firsthand. Using rotating platforms, folks got to spin and change their mass distribution/moment of inertia and feel the resulting change in angular velocity. Lower the moment of inertia by pulling mass closer to the axis of rotation and expect the angular velocity to increase – and, boy, did it ever. Tomorrow, we hit simple machines in preparation for Monday’s lab with pulleys and levers. Test is looking like it will fall on Wednesday, after all. Tomorrow – simple machines. Monday – lab. Tuesday – discuss lab and review. Wednesday – exam. There you have it…

Physical Science B reviewed the conceptual and mathematical aspects of conservation of energy and then turned this discussion into the conservation solely of mechanical energy. Because of friction, mechanical energy is not totally conserved in systems and this is the basis for evaluating the efficiency of a machine. Remember that a machine can’t be 100% efficient – the energy is never completely retained in mechanical form – and it can never, ever, exceed 100% efficiency. That would mean a creation of energy and energy conservation says that is a major-scale no-no. Tomorrow, your lab will allow you to get hands-on experience with energy conservation using as ball thrown into the air as our experimental system.

Physical Science E reviewed the basics of conservation of energy and then embarked on a series of problems that focus on conservation of mechanical energy. Take your time with these problems. Read them thoroughly, sketch them out, identify every piece of information that you are given, consider what quantities you might need to calculate and how the problem will let you do this. These take a bit more consideration than did last night’s homework problem, so budget your time accordingly. We’ll go over these in class tomorrow and then begin to discuss a practical application of conservation of energy – efficiency.

Physics F and G worked on test corrections, alone or with partners. Have them ready for me tomorrow and we will use the period tomorrow to begin moving into the relationship between work and simple machines.

Homework

Honors Physics A: None
Physical Science B: Read lab sheet. Complete Section Review 12.4 and the Graphing Skills on p. 409 by Monday
Physical Science E: Complete conservation of energy problems
Physics F and G: Complete test corrections