1 / 33

Energy and its Nature

Energy and its Nature. Energy. is the capacity to do ork. work. What is work ?. A force does  work  when it acts on a body so that the body is displaced in the direction of the force. Hawkeye does work on his bow by drawing it.

cree
Download Presentation

Energy and its Nature

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Energyandits Nature

  2. Energy is the capacity to doork. work.

  3. What is work ? • A force does work when it acts on a body so that the body is displaced in the direction of the force. Hawkeye does work on his bow by drawing it. Staff Sgt. Joshua Miles, Marine Drum & Bugle Corps marketing chief, thrusts a weighted bar over his head during the first part of the Civilian Military Combine at Bryce Resort, Va., April 21, 2012.

  4. Constant force in direction of straight-line displacement • The unit for Work is the joule. • 1 joule = 1 N●m

  5. Analyze Work Force Force Motion Motion

  6. Doing Work?

  7. Analyze Work Forward Force Total Force Downward Force Motion

  8. Sample Problems

  9. Sample Problems

  10. Seatwork • The painter lifted a load for a distance of 75 cm and the work done by the painter is 38 J. What is the mass of the load? • A load of 5-kg mass was lifted by the man and the total work done is equal to 40 J. By what distance was the load lifted?

  11. Energy is the capacity to doork. work.

  12. Energy Transfer

  13. LAW OF CONSERVATION OF ENERGY • Energy is neither • created nor destroyed, • it is just transformed. • The only thing that changes is the form in which it appears.

  14. Types of Energy • Kinetic Energy • – energy of motion • – increases when object moves faster • – increases as mass of object increases • Potential energy • – energy of position • – stored energy • – increases as mass of object increases

  15. Types of Energy • Kinetic Energy • Potential energy (gravitational) (elastic)

  16. Work and Potential Energy

  17. Work and Potential Energy Gravitational Potential Energy

  18. Work and Potential Energy Gravitational Potential Energy (10 N Ball) 3 m 5 m (a) (b) (c)

  19. Sample Problem A person’s heart and head are 1.3m and 1.8m above the feet, respectively. Determine the potential energy associated with 0.50 kg of blood in the heart relative to a.) the feet, b.) the head.

  20. Work and Kinetic Energy

  21. Work and Kinetic Energy

  22. Sample Problem 1.) A 7.00-kg bowling ball moves at 3.00 m/s. How fast must a 2.45-g Ping-Pong ball move so that the two balls have the same kinetic energy?

  23. LAW OF CONSERVATION OF ENERGY • Energy is neither • created nor destroyed, • it is just transformed. • The only thing that changes is the form in which it appears. for an isolated system

  24. The Work-Energy Theorem • The work done on an object by a net force equals the change in kinetic energy of the object

  25. Why do you run out of breath when running up stairs but not when walking up, when in fact the work done in both running and climbing up the stairs is the same?

  26. What is power? • Power is the measure of how fast the work is done. It is the rate at which energy is changed from one form to another. The unit for Power is the Watt. 1 Watt = 1 joule/second 1 hp = 745.70 watts

  27. Sample Problems An electric lift can raise a 500.0 kg mass a distance of 10.0 m in 5.0 s. What is the power of the lift?

  28. Seatwork # 6 1(a) How many horsepower is a 1400 W blow dryer? (b) How many watts is a 3.5 hp lawnmower? 2.An electric hoist does 196,000 J of work in raising a 250.0 kg load. How high was the load lifted?

  29. end

  30. Homework15 May 2014 Answer the problems. Show your solutions. ● Present your answers on ½ of a Letter or A4 sized sheet of unlined paper.

  31. 1. • A circus diver at the top of a pole has a potential energy of 8820 J. If the diver has a mass of 45 kg, what is the height of the pole? • Fill in the kinetic and potential energies asked for in the illustration on the right. • What is the diver’s speed just as he hits the water?

  32. 2. • A pendulum is displaced so that it has a potential energy of 10 J. Once the bob is released, the potential energy is converted into kinetic energy. • Fill in the kinetic and potential energies asked for in the illustration.

  33. 3. • A mass hangs above the floor on a copper wire. When a lit candle is moved along the wire and warms it, what happens to the height of the wire from the floor? Why? • If a cube of ice was used to cool the wire, how would it affect the height of the mass from the floor? Why?

More Related