| Week of | Aug 23
| Sep 6
| Oct 2
| Nov 6
| Phy 205 page |
| Aug 28 | Sep 11 | Oct 9 | Nov 13 | ||
| Sep 18 | Oct 16 | Nov 20 | Notes for Fall, 1999 | ||
| Sep 25 | Oct 23 | Nov 27 | |||
| Oct 30 |
23 Oct Review of the relationship between forces and potential energies:
This leads to a conservation form of the work-kinetic energy theorem:
I spent some time interpreting this and showing how you can use this to get a qualitative understanding of the motion of a mass subject to such a force. One example was the motion of the atoms in an H Cl molecule. If the molecule is disturbed, the atoms can vibrate about their equilibrium position. If they are disturbed enough, the molecule can be broken apart (dissociation).
Another example, one that we will be able to do quantitatively, involves a mass hanging on a spring. The potential energies come from gravity and from the force by the spring.
Branching over to another subject, work and energy in three dimensions. Tipler tries to make too large a leap, from one dimension constant force to three dimensions non-constant force. I prefer to separate the issues. One dimensional non-constant force is what I have spent the last couple of days on. Now, examine three dimensional constant force.
To do this, i went back to the same sort of analysis that led me to the work-energy result in the first place. I manipulated the basic (constant) force equation and its results into the relation
This is where the dot product appears.
25 Oct A brief recapitulation of the basics of kinetic and potential energies, restating the meaning of the dot product and its interpretation.
Various forms that energy can come in: kinetic, potential, heat, light,
sound, chemical, mass, ...
Some of these are really variations on the same idea, for example heat
in a gas is just the random motion of molecules, so it is just a form of
kinetic energy. It is however convenient to treat it as if it is
different.
The example of a cart going through a toy roller-coaster. Show the demo, and then work out what is needed so that the cart will go all the way over the top without falling off the tracks. I used both conservation of energy and F=ma.
Power. Its definition as dW/dt and then a discussion of the various units that it (and energy) come in.
27 Oct
Power of just living: metabolism. This depends on the individual, but
an average value is somewhere around 2000 kcal per day. The kcal,
kilocalorie, is the dietician's Calorie. To compare this metabolic
power to something else, I have to convert it to a standard set of
units, the Watt = Joule per second.
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Collisions. Look at inelastic collisions again, but this time examine the results for the energy loss. After solving for the final velocity, compute DK = Kafter - Kbefore.
Look at various special cases to see if the result makes sense, and also to learn what it's trying to tell us.
