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Chapter 15

Chapter 15. Energy. Chapter 15.1. Energy and Its Forms. Energy and Work. Energy is the ability to do work. Work is the transfer of energy Both use the SI Unit = J. Kinetic Energy. Potential Energy. Elastic Potential Energy. Gravitation Potential Energy. Chemical Potential

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Chapter 15

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  1. Chapter 15 Energy

  2. Chapter 15.1 Energy and Its Forms

  3. Energy and Work • Energy is the ability to do work. • Work is the transfer of energy Both use the SI Unit = J

  4. Kinetic Energy Potential Energy Elastic Potential Energy Gravitation Potential Energy Chemical Potential Energy How is all energy divided? All Energy

  5. To sum that up……

  6. The ability or capacity to do work. Measured by the capability of doing work: potential energy or the conversion of this capability to motion: kinetic energy.

  7. Identify the pictures Label them as: • Work (W) • Kinetic energy (KE) • potential energy (PE) PE KE W

  8. Potential Energy (PE) An objects PE can store energy as the result of its position.

  9. Or simply……. Energy that is stored and waiting to be used later

  10. Examples of Potential Energy: Stretching a rubber band.. -Stores energy Water at the top of a waterfall.. -Stores energy Yo–Yo in held in your hand.. -Stores energy because of position Drawing a Bow… -Stores energy because of position

  11. Determine the PE • The PE at the top of the tall platform is 50 J. Determine the PE at the other positions shown on the stair steps and the incline.

  12. Check your work 40 30 20 10 0 0

  13. Another formula! Formula for Potential Energy - PE = m x g x h • m= mass and labeled as…. • g= gravity (use 10 m/s2) • h= height and labeled as….. kg m

  14. Practice problem #1 A cart is pulled at constant speed along an inclined plane to the height of a seat-top. If the mass of the cart is 3.0 kg and the height of the seat top is 0.45 meters, then what is the potential energy of the cart at the height of the seat top. Set up your formula Plug in the “knowns” Solve the question.

  15. Check your answer SET UP KNOWNS PE = ? m = 3 kg g = 10 m/s2 h = 0.45m SOLVE THE EQUATION PE = m x g x h PE= (3 kg ) X (10 m/s2) X (0.45 m) PE = 13.5 J

  16. Kinetic Energy (KE) Energy an object has due to its motion

  17. Examples of Kinetic Energy… Shooting a rubber band. Water falling over the fall. A Yo-Yo in motion. Releasing the arrow from the bow.

  18. And because you love them so much…… Another formula! Formula for Kinetic Energy – KE = .5 x m x (v)2

  19. Practice problem #2 Determine the kinetic energy of a 1000-kg roller coaster car that is moving with a speed of 20.0 m/s.  KE = 0.5 x m x (v)2 Set up your formula Plug in the “knowns” Solve the question.

  20. Check your answer SET UP KNOWNS KE = ? m = 1000 kg v = 20 m/s SOLVE THE EQUATION KE = 0.5 x m x (v)2 KE= (.5) X (1000) X (20)2 KE = 200,000 J

  21. Practice problem #3 Determine the kinetic energy of a 1000-kg roller coaster car that is moving with a speed of 20.0 m/s. If the roller coaster car were moving with twice the speed, then what would be its new kinetic energy?  KE = 0.5 x m x (v)2 Set up your formula Plug in the “knowns” Solve the question.

  22. Check your answer SET UP KNOWNS KE = ? m = 1000 kg v = 40 m/s SOLVE THE EQUATION KE = 0.5 x m x (v)2 KE= (.5) X (1000) X (40)2 KE = 800,000 J Notice: When the speed is doubled then the KE is quadrupled!!

  23. Practice problem #4 In the summer, Ms. Lolich is a platform diver for the Ringling Brother’s Circus. If her kinetic energy of 15,000J just prior to hitting the bucket of water and her mass is 50kg, then what is her speed?  KE = 0.5 x m x (v)2 Set up your formula Plug in the “knowns” Solve the question.

  24. Check your answer SET UP KNOWNS KE = 15,000 J m = 1000 kg v = ? SOLVE THE EQUATION KE = 0.5 x m x (v)2 15,000 = (.5) X (50) X (?)2 15,000 = 25 X (?)2 15,000 = 25X (?)2 2525 600 = (?)2 round answer v = 25 m/s

  25. Determine the KE The diagram below depicts the motion of Ms. Lolich on a Friday night at Pine Knob as she glides down the hill and makes one of her record-setting jumps. The two forms of energy MUST sum up to 50 000 Joules.

  26. Check your work 0J 20 000 J 30 000 50 000 J 0 J

  27. Forms of energy… • Mechanical – car, ball, spring • Thermal – burner on a stove • Chemical - gasoline, coal, fireworks • Electrical – flashlight, iPOD • Electromagnetic – music on the radio, light, X-ray (you know them all!) • Nuclear - sun, power plant

  28. Video Review

  29. End of Section 15.1

  30. Chapter 15.2 Energy Conversion and Conservation

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