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Energy

Ms. Moore 10/1/12. Energy. What is energy?. Energy is required for any change that occurs, no matter how small. Energy is the ability to cause change. Examples: Forms of energy: Electrical Chemical Radiant Thermal Energy can be stored and move from place to place. Kinetic Energy.

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Energy

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  1. Ms. Moore 10/1/12 Energy

  2. What is energy? • Energy is required for any change that occurs, no matter how small. • Energy is the ability to cause change. • Examples: • Forms of energy: • Electrical • Chemical • Radiant • Thermal • Energy can be stored and move from place to place.

  3. Kinetic Energy • Kinetic energy (KE) is the energy a moving object has because of its motion. • The kinetic energy of a moving object depends on an object’s mass and its speed. Kinetic energy (joules) = ½ mass (kg) x speed2 (m/s)

  4. Practice Problems • A baseball with a mass of 0.15kg is moving at a speed of 40m/s. What is the baseball’s kinetic energy? • A sprinter has a mass of 80kg and a kinetic energy of 4,000 J. What is the sprinter’s speed? • A car with a mass of 1,500kg doubles its speed from 50km/h to 100km/h. By how many times does the kinetic energy of the car increase?

  5. Lab • Read the mini lab found on page 103. • Create a table of your results and be ready for a discussion. • How did the take off speed of the nickel depend on the distance that you stretched the rubber band? • How did the KE of the nickel depend on the distance the rubber band was stretched?

  6. Potential Energy • Energy doesn’t have to involve motion. Motionless objects have energy. • Potential energy (PE) is stored energy due to position. • Examples:

  7. 3 Types of PE: • Elastic potential energy is energy stored by something that can stretch or compress • Rubber band or spring • Chemical Potential Energy is energy stored in chemical bonds • Food and gasoline

  8. Gravitational Potential Energy (GPE) is energy stored by objects due to the position above Earth’s surface. • Depends on the objects mass and height above the ground. GPE (j) = mass (kg) X 9.8 (m/s2) X height (m)

  9. Practice Problems • Find the GPE of a coffee mug with a mass of 0.3kg that is on a counter top 1m high above the ground. • How high above the ground is a baseball with a mass of 0.15kg that has a GPE of 73.5J? • A rock climber is 200m above the ground and has a GPE of 117,600J. What is the rock climber’s mass?

  10. Lab: Bouncing Balls • Why do bouncing balls stop bouncing? • Refer to page 106 • Measure tennis ball vs. bouncy ball • Include a table of results

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