Notes

Chapter 8
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8-1
Conservative force - work is store in the form of energy that can be released at a later time.
Gravity mg is exerted at a constant speed through height g
W=Mgh when the box is dropped it gives the box and equivalent amount of kinetic energy back
Nonconservative force- Cannot be recovered later as kinetic energy
Friction ( Floor, Air resistance) Tension in a rope Sliding the box will result in friction that cannot be recovered later. The box does not move when you let it go.
The force you exert with friction is mu (mg)
The work you exert is mu mg d
Figure 8-3 W the work done is zero because the work done to move the box through the system amounts to zero because gravity does positive work on the box when released while picking it up does negative work
Conservative Force- force that does zero work on any closed path
Work done on the closed friction path is -4mu mg d
Conservative forces have work done from A to B as independent to the path.
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8-2
Potential energy and the work done by conservative forces
When the ball is lifted to a new position, it has potential energy, U, which can be converted into kinetic energy when the ball falls.
Only conservative forces have work stored as potential energy
Work of conservative force is negative change in U