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Potential and Kinetic Energy and the Conservation of Energy

Potential and Kinetic Energy and the Conservation of Energy. Pioneer High School. Energy. Energy is the capacity or actuality of change Energy can be stored Energy can be used When energy is used something changes

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Potential and Kinetic Energy and the Conservation of Energy

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  1. Potential and Kinetic Energy and the Conservation of Energy Pioneer High School

  2. Energy • Energy is the capacity or actuality of change • Energy can be stored • Energy can be used • When energy is used something changes • When energy is stored, that means later on, if the stored energy is released, something could change without any outside source of energy to help it out

  3. Energy • Measured in Joules (J) • Examples of types of energy: • Chemical energy, oil, food, batteries • Electrical energy, power plants • Heat energy, steam engine, fire • Nuclear energy, reactors, bombs • Mechanical energy, springs, machines • Light energy, light bulbs, the Sun

  4. Potential Energy • Potential Energy = the energy stored in an object • Examples • Chemical potential energy in a battery • Nuclear potential energy in an Atom Bomb • Magnetic potential energy of two like poles touching

  5. Gravitational Potential Energy • Gravitational potential energy = the energy an object has because of its height above the surface of the Earth.

  6. Gravitational Potential Energy • Formula to calculate Potential energy: PE = mgh m = mass g = 9.81m/s2 h = height of the object above the ground PE is the potential energy

  7. Sample Problem A 70kg cliff diver stands on a 45m cliff. How much potential energy does the diver have?

  8. Kinetic Energy • The energy of motion • When an object is moving it has energy • It takes energy to make something move

  9. (Vf2 - Vi2) 2 Kinetic Energy • Kinetic energy formula: • KE = work done to speed something up • KE = W = mad • But we want a formula in terms of mass and velocity • Vf2 = Vi2 + 2ad • So, ad =

  10. (Vf2 - Vi2) 2 Kinetic Energy W = m ad ad =

  11. W = m (Vf2 - Vi2) 2 Kinetic Energy W = ½ mVf2 – ½ mVi2 So the term for kinetic energy became, KE = 1/2mv2

  12. Kinetic Energy • Sample Problem: How much kinetic energy is in a .050kg bullet going 400m/s?

  13. Conservation Of Energy • In a closed system, energy can not be created or destroyed.

  14. Conservation Of Energy • All the balls started with potential energy

  15. Conservation Of Energy • After dropping to the ground the potential energy had turned into kinetic energy

  16. Conservation Of Energy • And when they bounce into each other, they exchange equal amounts of kinetic energy, so they do not lose any overall

  17. Examples of Conservation • A flowerpot falls : PEtop = KE bottom PE top KE bottom • A bullet shot into the air: • KE bottom = PEtop

  18. Conservation formula PE = KE mgh = ½ mv2 gh = ½ v2 h = v2 v = √2gh 2g

  19. Sample problems A 1.0kg flowerpot falls from the ledge of a window 15.0m above the ground. How fast must the pot be going when it hits the ground?

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