Student "edition" found at {csi dot journalspace dot com}.

Maybe I shouldn't have started this blog now, not with everything that's been going on.

In the first meeting of my mechanics lecture class for the thirteenth week of the second term, I discussed the Conservation of Mechanical Energy.

First I defined the rule, which is that in any closed system with no external forces, the total energy at any point and at any time for the system remains constant.

I next gave the unit of energy, which is joule, and its two equivalents, which is Newton-meter and kilogram meter-squared over second-squared.

Then I gave the two forms of energy we would be dealing with, and their equations. Kinetic energy is equal to one half the mass multiplied by the square of the velocity. Gravitational potential energy is the mass times the acceleration due to gravity times the height.

I even gave them an example of another type of potential energy, which is elastic, or what is stored in a stretched rubber band or a compressed spring.

Then I gave the equation for total energy, which is, of course, kinetic plus potential.

Lastly I gave the same example that I have been giving for the last three times I have taught this course, which is the free fall dropped ball (hey, that rhymes!) where potential energy starts at maximum (at the highest point) and kinetic energy starts at zero. So total energy at that point is equal to the potential energy.

Then at each point below that, kinetic energy increases as the velocity increases and the potential energy decreases as the height decreases, but the total energy still remains the same.

Finally at the end, the potential energy is zero just before the ball hits the ground, so kinetic energy is equal to the total energy. Thus all the potential energy is converted to kinetic energy.

Another example I gave was a frictionless slide, and the third was projectile motion with the angle not given. I told them they could use the old methods to solve these if they wanted, whichever for them was easier.

Session 901 has no potential. Class dismissed.