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Journal #5

Journal #5. Write all of the types of energy you think the basketball Ms. C is playing with has. Sec. 9-1 "What is Energy" pp. 240-249. Energy and Work: Working Together. Energy is the ability to do work .

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Journal #5

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  1. Journal #5 • Write all of the types of energy you think the basketball Ms. C is playing with has

  2. Sec. 9-1 "What is Energy"pp. 240-249

  3. Energy and Work: Working Together • Energy is the ability to do work. • Work is done when a force causes an object to move in the direction of the force.

  4. Energy and Work: Working Together • When one object does work on another object, energy is transferred from the first object to the second object. • a). This energy allows the second object to do work. • b). So, work is the transfer of energy. • c). Energy is expressed in units of joules (J).

  5. How do energy and work help you play tennis? • The racket does work on the ball and the ball does work on the net.

  6. Kinetic Energy • Kinetic energy is the energy of motion. • All moving objects have kinetic energy. • Like all forms of energy, kinetic energy can be used to do work, such as allowing a hammer to do work on a nail.

  7. Kinetic Energy Depends on Mass & Speed • An object’s kinetic energy (KE) can be found by the following equation: KE = mv² 2 • The m stands for the object's mass in kg; • The v stands for the object's speed. • Speed has a greater effect on kinetic energy than mass does because speed is squared • A car moving 50 mph has 4 times the kinetic energy of a car going 25 mph!

  8. What is the relationship between mass, speed, and kinetic energy? • If mass and speed increase, kinetic energy increases. • What happens to KE if mass doubles? If speed doubles? Remember KE = mv² 2 • If mass doubles, KE doubles; if speed doubles, KE quadruples.

  9. Complete Math Focus on Page 241

  10. Gravitational Potential Energy • When you lift an object you transfer energy to the object and give it gravitational potential energy. • Examples of objects that have gravitational potential energy (GPE) include books on a shelf and a backpack on your back. • The amount of GPE that an object has depends on its weight and its height.

  11. Calculating GPE • Gravitational potential energy is found by using the following equation: GPE = weight x height • GPE is expressed in newton-meters, or joules (J ). • Remember that weight is the amount of force (N) that must be used on an object to lift itand that height is adistance. • So, GPE is equal to the work done on an object to lift it to a certain height.

  12. Complete Math Focus on Page 242

  13. Mechanical Energy • Mechanical energy is the total energy of motion and position of an object. • Mechanical energy can be all potential energy, all kinetic energy, or some of each. • Mechanical energy can be found using the following formula: • Mechanical Energy = potential energy + kinetic energy

  14. Mechanical Energy • Mechanical energy of an object remains the same unless it transfers some of its energy to another object • Even if mechanical energy stays the same, potential and kinetic energy can increase or decrease.

  15. Mechanical Energy in a Juggler’s Pin • As a pin leaves a juggler’s hand, the pin’s kineticenergy transfers to potential energy . • The pin slows down as it moves upward, which means kinetic energy is decreasing.

  16. Mechanical Energy in a Juggler’s Pin • The pin stops moving when all the kineticenergy turns into potential energy. • As the pin falls and speeds up, more and more of its potential energy is changed back into kineticenergy.

  17. Journal #5 (again) • After learning about PE, KE and ME, add any info to your journal that you feel is necessary

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