The Various Faces of Energy

Honors Physics took time to discuss their conservation of energy lab and it seems that most groups got very nice results. A clear linear relationship between applied force and displacement to obtain the spring constant and clean sine functions to describe the oscillation of the mass-spring system. Energy was well conserved in the tests, with the addition of the index card demonstrating the transformation of energy to a non-conservative form (heat). We then went over the last exam and began a discussion of potential energy. We hit gravitational potential energy today and will continue on with that tomorrow, including, as well, elastic potential energy.

Physical Science B and E reviewed for their Chapter 11 exam. It still seems that a lot of folks are having trouble with the math portion. Don’t forget to ask for extra help or extra problems to work when you are having difficulty with a concept. Don’t wait until the day before the test, either. Get help as soon as you are having problems. Often, in this course, concepts reinforce each other – if you are having difficulty with one, you will likely have difficulty with others in the chapter/course.

Physics F discussed conservation of mechanical energy today. When we talk about mechanical energy, we mean kinetic energy and any forms of potential energy available. For our purposes, that will be either gravitational or elastic potential energy. In a system where friction is negligible, we expect the total amount of mechanical energy to remain constant in a system, although it can be converted repeatedly between forms/types. When friction is significant, we expect to see a reduction in the total amount of usable mechanical energy in the system. Tomorrow’s lab will allow you to see how energy is converted between potential/kinetic in a mass-spring system and how the total amount of energy changes with and without significant frictional resistance.

Physics G conducted their conservation of energy lab today and preliminary results look good. The first part of the lab allowed you to calculate the spring constant for your individual spring, which is required if we are going to assess elastic potential energy. The second part of the activity allowed you to visualize the motion of the spring through time and evaluate the energy changes associated with that motion. Simple harmonic motion exists in many oscillating systems like springs and pendulums and the plot of displacement vs. time makes a nice sine curve, like groups found for their system. As you consider your results and write the conclusion for your lab, think about what is happening in each piece of the displacement graph (in terms of both position and velocity) and why you got the pattern you witnessed for your energy plots. We will discuss your lab tomorrow and use it to illustrate our discussion of conservation of energy.

Homework

Honors Physics A: 5D and 5.2 Section Review
Physical Science B and E: Review for exam
Physics F: Read lab sheet. Complete 5.3 SR #2,3 and p. 195 #30-34 for Wednesday
Physics G: Complete lab write up. Complete 5.3 SR #2,3 and p. 195 #30-34