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Thursday, February 16th

Thursday, February 16th. Mechanical Energy. Today’s Goals. Goal 1: SWBAT use the Law of Conservation of Energy to explain why a situation in which mechanical energy is lost cannot be possible. Goal 2: SWBAT determine points of high KE or PE and low KE or PE in real-life situations.

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Thursday, February 16th

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  1. Thursday, February 16th Mechanical Energy

  2. Today’s Goals • Goal 1: SWBAT use the Law of Conservation of Energy to explain why a situation in which mechanical energy is lost cannot be possible. • Goal 2: SWBAT determine points of high KE or PE and low KE or PE in real-life situations.

  3. Law of Conservation of Energy– energy cannot be created or destroyed; total amount of energy in the universe does not change  • What else have you learned is always conserved?

  4. What Else is Conserved? • Momentum • Mass

  5. Law of Conservation Example Car Vibrates = Kinetic Energy Car heats up = heat energy Your Heater or AC = energy not going to moving forward Chemical Energy in Gasoline

  6. Mechanical Energy • Mechanical Energy – total amount of potential and kinetic energy in a system • So, ME = Kinetic E + Potential E • Remember there are 3 different types of Potential Energy! • So, Mechanical E depends on the motion of an object (kinetic) and the position of the object (potential)

  7. Golf Swing Example

  8. Sling Shot Example

  9. Bungee Jump Example

  10. Question 1 • Which of the following examples has kinetic energy converting into potential energy? • A) A boulder rolls down a hill • B) A ball is thrown upward • C) A swing comes to a stop • D) A bowling ball rolls horizontally B!

  11. Question 2 • The Gravitational Potential Energy of an object changes when which of the following changes? • A) The object’s speed • B) The object’s mass • C) The object’s temperature • D) The object’s length B! (GPE = mgh)

  12. Question 3 • The Kinetic energy of an object changes when which of the following changes? • A) The object’s chemical potential energy • B) The object’s volume • C) The object’s direction of motion • D) The object’s velocity D! (KE = ½ mv2)

  13. Question 4 • When an energy transformation occurs, which of the following is true? • A) Mechanical energy doesn’t change. • B) Mechanical energy is lost. • C) The total energy doesn’t change. • D) Mass is converted into energy. C!

  14. As a group: • Turn to page 150 in your text books. • Complete questions #1-9 on separate piece of paper. EACH PERSON NEEDS OWN PAPER • Things that will HELP YOU: • Gravity = 9.8 m/s/s • K E = ½ mv2 • GPE = mgh (and m = PE/gh) • For #8: The baseball’s velocity slows as it goes UP, and speeds up as it goes DOWN

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