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# Potential Energy and Energy Conservation

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Physics for Secondary Teachers I Report on Potential Energy and Energy Conservation

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### Potential Energy and Energy Conservation

1. 1. POTENTIAL ENERGY AND ENERGY CONSERVATION Reported by: Ida Lyn A. Azuelo BSED Physics 3 Physics for Secondary Teachers 1
2. 2. Potential Energy • The energy associated with the position of a system rather than its motion
3. 3. Gravitational Potential Energy • Potential energy associated with a body’s weight and its height above the ground
4. 4. m – mass of the body s – displacement y - vertical components w – weight (mg) Fother - some forces acting on the body
5. 5. m – mass of the body s – displacement y - vertical components w – weight (mg) Fother - some forces acting on the body The quantity (y1 –y2) is negative, and Wgrav is negative because the weight and displacement are in opposite direction.
6. 6. Gravitational Potential Energy
7. 7. Conservation of MechanicalEnergy (Gravitational Forces Only) Work- Energy TheoremWtot = ΔK = K2 - K1 Wtot = Wgrav = -ΔUgrav = Ugrav,1 - Ugrav,2 ΔK = -ΔUgrav K2 - K1 = Ugrav,1 - Ugrav,2 K1 +Ugrav,1 = K2 + Ugrav,2 If only gravity does work
8. 8. E = K + Ugrav Potential energy kinetic energy E1 = K1 + Ugrav,1 E2 = K2 + Ugrav,2
9. 9. When only the force of gravity does work, the total mechanical energy is constant— that is, it is conserved. CONSERVATION OF MECHANICAL ENERGY
10. 10. Problem Sample You throw a 0.145-kg baseball straight up, giving it an initial velocity of magnitude 20.0 m/s. Find how high it goes, ignoring air resistance.
11. 11. When ForcesOther Than Gravity Do Work Wother + Wgrav = K2 - K1 Wgrav = Ugrav,1 - Ugrav,2 Wother + Ugrav,1 - Ugrav,2 = K2 - K1 K1 +Ugrav,1 = K2 + Ugrav,2 If forces other than gravity do work
12. 12. Elasticpotential energy • The process of storing energy in a deformable body such as a spring or rubber band in terms of elastic potential energy. • A body is called elastic if it returns to its original shape and size after being deformed.
13. 13. F = kx F – force on the spring k - force constant of the spring x - displacement
14. 14. Work done on a spring Work done by a spring
15. 15. Elastic Potential Energy
16. 16. The work done by all forces other than the gravitational force or elastic force equals the change in the total mechanical energy E = K + U of the system, where U = Ugrav + Uel is the sum of the gravitational potential energy and the elastic potential energy.
17. 17. Conservative Force and nonConservativeForce A force that offers this opportunity of two-way conversion between kinetic and potential energies A force that is not conservative
18. 18. Energy is never created or destroyed; it only changes form.
19. 19. THANK YOUFOR LISTENING!!!!
20. 20. POTENTIAL ENERGY AND ENERGY CONSERVATION Reported by: Ida Lyn A. Azuelo BSED Physics 3 Physics for Secondary Teachers 1