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Feynman Lectures on Physics:
Conservation of Energy
What is energy?
Imagine a child, perhaps "Dennis the Menace"
Energy is an abstract concept When all is calculated energy is
constant We see that the energy is the same
before and after but don’t understand why
What is energy?
“we have no knowledge of what energy is. We do not have a picture that energy comes in little blobs of a definite amount. It is not that way.”
There are many forms of energy and we have formulas for all of them to put in an equation
Gravitational Potential
“Let us also make a hypothesis: that there is no such thing as perpetual motion”
Can consider a weight balance machine GPE = Weight X Height
Reversible machine = XNormal machine = Y
Y is less than X otherwise perpetual motion!!
3mX=m3X
Kinetic Energy
“Of course, the fact that motion has energy has nothing to do with the fact that we are in a gravitational field. “
In the case of kinetic energy a pendulum can be considered
KE=weight X height A formula is needed that
relates velocity to height Turns out to be KE=WV2/2g
Other types of energy
“Ordinarily when things roll, there is bumping and jiggling because of the irregularities of the material ”
Consider a Spring Adding the weight X heights
doesn’t check out! Something needs to be added Spring stops moving after a time
There are many types of energy like light, heat, radiation etc.