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Energy. . Energy is defined as the capacity to do mechanical work . Forms of energy Kinetic Energy (KE) : energy of motionA moving carRotating shaft Potential Energy (PE): stored energy or energy of position Gravitational potential energyA ball positioned above the ground Elastic potentia
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1. Phys1111 Chapter 6
Energy and Work
2. Energy
3. Energy
4. Energy Energy transfer or conversion:
Energy is a conserved quantity, that is, the total amount of energy in the universe is a constant.
Energy is not created or destroyed but can be:
Transferred from one object (or system) to another
(a bat transfers energy to a ball, Sun transfers energy to Earth, etc.)
Converted (transformed) from one form to the other
(electrical to mechanical, chemical to electrical, mechanical to heat, etc.)
5. Work work is
the mechanical transfer of energy to or from a system by external forces.
expressed as the product of a force and the distance through which it moves a body in the direction of that force
6. Work
7. Work
8. Work
9. Work
10. Work
11. Kinetic Energy
12. Kinetic Energy
13. Kinetic Energy
14. Gravitational Potential Energy
15. Gravitational Potential Energy
17. Energy of a falling object
18. Energy of a falling object
19. Energy of a falling object
20. Energy of a falling object
21. Energy of a falling object
22. Path independence of Gravitational potential energy
23. The Law of Conservation of Energy
24. The Law of Conservation of Energy Generally energy is transferred in two ways:
as a heat (Q) – because of the temperature difference between the two objects.
as work done (Wext ) by external force.
Q and Wext may be positive or negative.
positive Q and positive Wext mean energy is transferred into the system.
negative Q and negative Wext mean energy is taken out of the system.
25. The Law of Conservation of Energy Total energy (E) of a system is
26. The Law of Conservation of Energy
27. The Law of Conservation of Energy
28. Conservative and non-conservative forces A force is conservative force if the work done by this force is the same along any path connecting the same two points or equivalently, if the total work done by this force around any closed path (one that returns to its starting point) is zero.
29. Conservative and non-conservative forces For an object moving around a closed path
30. Conservative and non-conservative forces
31. Conservative and non-conservative forces
32. Conservative and non-conservative forces
33. Conservative and non-conservative forces
34. Conservative and non-conservative forces
35. Elastic Force
36. Elastic Potential Energy
37. Elastic Potential Energy Whenever we apply the conservation of energy and work-energy theorem, the potential energy of the system must include all kinds of potential energies.
38. Elastic Potential Energy
39. Energy Rates
40. Energy Rates If the energy transfer is accomplished by doing work W
41. Energy Rates
42.
Exercises
6.14, 6.16,6.19, 6.22, 6.27, 6.33,6.40, 6.41, 6.43, 6.46,6.47,
6.61, 6.84
