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Energy

Energy. What is energy?. Energy measures the ability for things to change themselves or to cause change in other things. . Units of energy. Pushing a 1-kilogram object with a force of one newton for a distance of one meter uses one joule of energy.

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Energy

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  1. Energy

  2. What is energy? • Energy measures the ability for things to change themselves or to cause change in other things.

  3. Units of energy • Pushing a 1-kilogram object with a force of one newton for a distance of one meter uses one joule of energy. • A joule (J) is the S.I. unit of measurement for energy.

  4. Joules • One joule is a pretty small amount of energy. • An ordinary 100 watt electric light bulb uses 100 joules of energy every second!

  5. Potential and Kinetic Energy Potential energy • capable of becoming active • stored energy • from the position of an object relative to Earth. potential energy = the mass times the acceleration due to gravity (9.8 m/s2) X the height

  6. Potential Energy mass of object (kg) height object raised (m) EP = mgh PE (joules) gravity (9.8 m/sec2)

  7. Potential and Kinetic Energy Kinetic energy • the energy of motion • depends on the mass of the object as well as the speed of that object • A moving cart has kinetic energy because it can hit another object (like clay) and cause change.

  8. Kinetic Energy KE (joules) mass of object (kg) EK = ½ mv2 velocity (m/sec)

  9. Some forms of energy Mechanical energy • is the energy possessed by an object due to its motion or its position. • Potential energy and kinetic energy are both forms of mechanical energy.

  10. Some forms of energy Chemical energy • is a form of energy stored in molecules. • Batteries are storage devices for chemical energy.

  11. Some forms of energy Electrical energy • comes from electric charge, which is one of the fundamental properties of all matter.

  12. More forms of energy Nuclear energy • is a form of energy stored in the nuclei of atoms. • In the Sun, nuclear energyis transformed to heat that eventually escapes the sun as radiant energy.

  13. More forms of energy Radiant energy • is energy that is carried by electromagnetic waves. • Light is one form of radiant energy.

  14. More forms of energy • The electromagnetic spectrum includes visible light infrared radiation (heat), and ultraviolet light. • Light energy and heat energyare included in the electromagnetic spectrum.

  15. Sources of energy • All objects with mass feel forces in the presence of Earth’s gravity. • These forces are a source of energy for objects or moving matter such as falling rocks and falling water.

  16. Conservation of Energy • The idea that energy tranforms from one form into another without a change in the total amount is called the law of conservation of energy. • The law of energy conservation says the total energy before the change equals the total energy after it.

  17. Conservation of Energy • Systems change as energy flows and changes from one part of the system to another. • Each change transfers energy or transforms energy from one form to another.

  18. Conservation of Energy • When you throw a ball in the air, the energy transforms from kinetic to potential and then back to kinetic.

  19. Potential and Kinetic Energy A 50 kg boy and his 100 kg father went jogging. Both ran at a rate of 5 m/s. Who had more kinetic energy? Show your work and explain. Solution:

  20. Potential and Kinetic Energy A 50 kg boy and his 100 kg father went jogging. Both ran at a rate of 5 m/s. Who had more kinetic energy? Show your work and explain. Solution:

  21. Potential and Kinetic Energy What is the potential energy of a 10 N book that is placed on a shelf that is 2.5 m high? Solution:

  22. Potential and Kinetic Energy 1. Determine the amount of potential energy of a 5.0-N book that is moved to three different shelves on a bookcase. The height of each shelf is 1.0 m, 1.5 m, and 2.0 m.

  23. Potential and Kinetic Energy 2. You are on in-line skates at the top of a small hill. Your potential energy is equal to 1,000 J. The last time you checked, your mass was 60.0 kg. a. What is your weight in newtons?

  24. Potential and Kinetic Energy 2. You are on in-line skates at the top of a small hill. Your potential energy is equal to 1,000 J. The last time you checked, your mass was 60.0 kg. b. What is the height of the hill?

  25. Potential and Kinetic Energy 2. You are on in-line skates at the top of a small hill. Your potential energy is equal to 1,000 J. The last time you checked, your mass was 60.0 kg. c. If you start rolling down this hill, your potential energy will be converted to kinetic energy. At the bottom of the hill, your kinetic energy will be equal to your potential energy at the top. Calculate your speed at the bottom of the hill.

  26. Potential and Kinetic Energy 3. A 1.0-kg ball is thrown into the air with an initial velocity of 30 m/s. a. How much kinetic energy does the ball have?

  27. Potential and Kinetic Energy 3. A 1.0-kg ball is thrown into the air with an initial velocity of 30 m/s. b. How much potential energy does the ball have when it reaches the top of its ascent?

  28. Potential and Kinetic Energy 3. A 1.0-kg ball is thrown into the air with an initial velocity of 30 m/s. c. How high into the air did the ball travel?

  29. Potential and Kinetic Energy 4. What is the kinetic energy of a 2,000-kg boat moving at 5.0 m/s?

  30. Potential and Kinetic Energy 5. What is the velocity of an 500-kg elevator that has 4000 J of energy?

  31. Potential and Kinetic Energy 6. What is the mass of an object traveling at 30 m/s if it has 33,750 J of energy?

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