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SP1. Students will analyze the forms and transformations of energy.

SP1. Students will analyze the forms and transformations of energy. Mechanical Energy. Energy. Energy is the ability to cause change Anything that changes uses energy Energy is measured in Joules (J), just like work One form of energy is Kinetic energy (KE). How much KE?.

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SP1. Students will analyze the forms and transformations of energy.

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  1. SP1. Students will analyze the forms and transformations of energy.

  2. Mechanical Energy

  3. Energy • Energy is the ability to cause change • Anything that changes uses energy • Energy is measured in Joules (J), just like work • One form of energy is Kinetic energy (KE)

  4. How much KE?

  5. How Much KE?

  6. Kinetic Energy (KE) • Moving energy • Dependent on • Mass Mass, KE • Velocity Velocity, KE

  7. Kinetic Energy (KE) • The equation for KE is KE = 1/2mv2 Because velocity is squared, the KE will go up very fast as you increase velocity

  8. Example • A 1,000kg truck was traveling at 4m/s and then accelerated to 10m/s. Find the initial KE and the final KE. KE = 1/2mv2 • KE = (½)(1000)(4)2 • KE = 8000J • KE = (½)(1000)(10)2 • KE = 50000J

  9. Potential Energy • Potential energy is stored energy • It comes in many forms: • Gravitational • Elastic • Chemical • Electric • Etc.

  10. What kind of PE?

  11. Gravitational Potential Energy (GPE) • Is the energy an object will use to fall. • Depends on the object’s : • Weight (mass * gravity) • Height from ground (or whatever it’s falling to) • Equation for GPE: PEg = mgh

  12. Problem • A 0.06 kg tennis ball starts to fall from a height of 2.9m. What was its gravitational potential energy at that height? • GPE = mgh • GPE = (0.06)(10)(2.9) • GPE = 1.74J

  13. Elastic Potential Energy • Elastic potential energy comes when an object is stretched or compressed. • This depends on how far the object has been distorted.

  14. Mechanical Energy Mechanical energy is the energy of a system • Mechanical energy (ME) comes from two different sources: • Potential energy • Kinetic energy • Mechanical energy typically does not include nuclear, chemical, electrical and other ancillary types of energy

  15. Conservation of Energy • In a system, the mechanical energy is conserved. • The amount of energy in the beginning should equal the amount of energy at the end* *minus energy loss due to friction

  16. Converting Energy • Mechanical Energy is the total of the potential and kinetic energy in a system. • ME = PE + KE GPE 0 KE GPE 0 KE 0 GPE KE GPE KE GPE KE

  17. Converting Energy • Though GPE and KE change, the total energy remains constant.

  18. Open vs. Closed Systems • A closed system is one where no energy is added • An open system does add energy

  19. Try It • The tops of the towers on the Golden Gate Bridge are 227m above the water. Suppose that a worker drops a 0.655 kg wrench from the top of the tower. What will be the kinetic energy of the wrench when it hits the water?

  20. Mass and Energy • Sometimes, mass can be converted into energy • Ex: Nuclear fission/fusion • The equation for the amount of energy produced is E = mc2

  21. Now it’s your turn! • Do the problems on the worksheet

  22. ToD • Name three types of energy transformations you’ve used today • Show your work

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