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Law of Conservation of Energy

Law of Conservation of Energy. Bowling Ball Demonstration. *Google Physics Bowling Ball Demonstration and watch a video that shows this demonstration (Contact Ms. K. if you aren’t sure you have the right one). Kinetic Energy. Energy due to an objects motion KE= ½mv 2

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Law of Conservation of Energy

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  1. Law of Conservation of Energy

  2. Bowling Ball Demonstration *Google Physics Bowling Ball Demonstration and watch a video that shows this demonstration (Contact Ms. K. if you aren’t sure you have the right one)

  3. Kinetic Energy • Energy due to an objects motion • KE= ½mv2 • Kinetic Energy = ½ (mass) X (velocity)2 • Velocity is the ONLY number that is squared • Energy is measured in Joules

  4. KE= ½ mv2 Step 1: write down all of your givens (any information the problem gives you) Step 2: Rewrite your equation Step 3: Substitute your givens for all variables possible Step 4: Solve the algebra problem * Don’t forget your units!!! Example: If mass of an object is 10kg and velocity is 5 m/s, what is the kinetic energy of the object? • Mass= 10kg • Velocity= 5m/s • KE= ? KE= ½ mv2 KE = ½ (10)(5)2 KE= 125 Joules

  5. Bowling Ball Demo. Check Your Understanding Where during the demonstration did you see kinetic energy? Where do you think kinetic energy was greatest? If the mass of the bowling ball is 5kg and the highest velocity it reached was 20m/s, what is the greatest Kinetic Energy the bowling ball reached?

  6. Gravitational Potential Energy • “Stored” energy due to an object’s position • GPE= mgh • Gravitational Potential Energy= (mass)X(9.8)X(height) • g is always 9.8 • Again, energy is measured in Joules

  7. PE=mgh Step 1: write down all of your givens (any information the problem gives you) Step 2: Rewrite your equation Step 3: Substitute your givens for all variables possible Step 4: Solve the algebra problem * Don’t forget your units!!! Example: a 3kg rock sits at the top of a cliff 100 meters high, how much gravitational potential energy does the rock have? mass=3kg g= 9.8 height= 100m GPE=? GPE=mgh GPE=(3)(9.8)(100) GPE=2,940Joules

  8. Bowling Ball Demo.Check Your Understanding During the bowling ball demonstration, where did the ball have gravitational potential energy? During the bowling ball demonstration, where was gravitational potential energy greatest? When the bowling ball had the greatest gravitational potential energy, did it have any kinetic energy? If the height of an object was 2m and the mass was 0.5kg, what is the gravitational potential energy of the object?

  9. Law of Conservation of Energy Energy is neither created nor destroyed, it is transferred from one type to another Total Energy= Kinetic Energy + Gravitational Potential Energy TE= KE + GPE The total energy in the system before an event equals the total energy after an event. (TE stays the same in the isolated system)

  10. TEbefore=TEafter The pendulum starts at position 1, swings to position 5 and back to position 1. At position 1 GPE=10Joules, how much KE is present at position 1? At position 2 the GPE has decreased to 5 Joules, how much KE is present at position 2? At position 3 GPE has dropped to is minimum of 0 Joules, how much KE is present? At position 4 KE has dropped back to 5 Joules, how much GPE is now present? At position 5, KE reaches is minimum as the pendulum prepares to swing back, how much GPE is present?

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