Chapter 8: Potential Energy & Conservation Of Energy Flashcards
What is potential energy?
The form of energy associated with the configuration of two or more objects that interact by means of a “special” force, often used as a book-keeping device. It can change forms–that is, go from potential, to kinetic, to back again.
Only certain, special forces known as ___ forces allow the exchange of energy between kinetic and potential, two examples of which being ___ force and ___.
Conservative; tension; gravity.
Gravitational Potential Energy: U(subg) = …
mgΔy
Elastic Potential Energy: U(subs) = …
(1/2)kx^2
If the object is moving in the direction OPPOSITE of the work, then the direction of the work is (positive)/(negative).
Negative
The mechanical energy of a system is …
The total energy of the system.
E(submec) = K + U(subtotal)
ΔE(mec) = 0 only when…
No external forces do work on the system, and when the only internal forces doing work are conservative forces. Kinetic frictional forces on internal surfaces are NOT external!
The relationship between work done by a conservative force and change in corresponding potential energy is as follows:
W(subc) = -ΔU
(Finding potential energy change by integrating force on a force vs. distance graph)
The relationship between potential energy and the rate of change of force:
F(x) = - (dU)/(dx)
If you have a plot of potential energy, then the force is the negative of ___.
The slope of the tangent line
TRUE or FALSE: The total E of a system can change only by amounts of energy that are transferred to or from the system.
True!
The General Energy Principle states that…
W(ext) = ΔE(submec) + ΔE(subthermal) + ΔE(subint)
ΔE(subthermal) is equal to…
|f(arrowsubk)| * d
What is an isolated system?
A system in which there is no external work acting on the system.
When it is an isolated system AND there are no rough surfaces sliding, then ΔE(submec) = …
0
