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Understanding Energy: Kinetic, Potential, and Work Explained

Learn about energy types - kinetic and potential, work in physics, calculations, and examples with practical applications explained. Discover how forces, distance, and motion contribute to the concept of energy.

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Understanding Energy: Kinetic, Potential, and Work Explained

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  1. Energy What is it?

  2. What is it? • Here are some examples:

  3. Definition • Energy is the ability to cause change • Two types of energy • Kinetic • Potential

  4. Kinetic • Energy in the form of motion • Running • Throwing • Flying • How much kinetic energy depends on what? • Mass and Velocity • Question: What has more kinetic energy: a truck traveling at 100 km/hr or a motorcycle traveling at 100 km/hr • How about a truck traveling at 100 km/hr or a truck traveling at 80 km/hr

  5. Potential Energy • Stored Energy • Students sitting in their seats • A bullet in a gun • Battery • Potential energy changes into kinetic energy

  6. Work • Transfer of energy through motion • In order for work to take place, a force must be exerted through distance • Calculating Work: • Work = Force x Distance or W = F x D

  7. Units • Work is expressed in Newton-meters (N x m) Or Joules (j) Named after British Scientist James Prescott Joule

  8. Example • A student’s full backpack weighs 30 N. She lifts it from the floor to a shelf 1.5 m high. How much work is done on the pack full of books? • W = F x D • F= 30 N • D = 1.5 m • W = ? • W= 30N x 1.5 m • W = 45 N x m or 45 J

  9. Try This One • A carpenter lifts a 4.5 kg beam 1.2 meters. How much work is done on the beam? • What do you know? • Distance = 1.2 m • Force = ? You must calculate force • F = M x A M = 4.5 kg A = ? • A = gravity = 9.8 m/s2 • F = 4.5 kg x 9.8 m/s2 F = 44.1 N • W = 44.1N x 1.2 m W = 52.92 J

  10. Another Example • A man pushes a lawnmower with a force of 500 N for 200 m. How much work is this if the force of friction acting on the lawnmower is 150 N? • W = F x D • F = 500 N + 150 N • D = 200 m • W = 650 N X 200 m • W = 130000 Joules

  11. One more example • Cheerleader A is holding up cheerleader B. Cheerleader B is exerting a force a 80 N on cheerleader A. If cheerleader A walks forward 2 meters while holding cheerleader B, how much work has cheerleader A done? • No work!!!! Why? • Because work was not done over a distance • W = F x D • W = 80 N x 0 m • W = 0 N x m or 0 Joules

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