1 / 14

Chapter 10

Chapter 10. Energy, Work, and Simple Machines. 10.1 Energy and Work. Energy is the ability to produce change in itself or the environment. Energy of Motion: v f 2 = v i 2 + 2 ad Rearranging v f 2 - v i 2 = 2 ad Substituting Newton’s second law v f 2 - v i 2 = 2 Fd/m.

kalar
Télécharger la présentation

Chapter 10

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. Chapter 10 Energy, Work, and Simple Machines

  2. 10.1 Energy and Work • Energy is the ability to produce change in itself or the environment. • Energy of Motion: vf2 = vi2 + 2ad Rearranging vf2 - vi2 = 2ad Substituting Newton’s second law vf2 - vi2 = 2Fd/m

  3. Multiply both sides by ½ m ½ mvf2 – ½ mvi2 = Fd • Kinetic energy KE = ½ mv2 • Work-Energy Theorem ΔKE = W • When work is done on an object, a change in kinetic energy results.

  4. Work: • Through the process of doing work, energy can transfer from the environment to the object and back again! • The equation for work is • W = Fd For constant forces in the direction of the motion. Unit of work is the joule (J)

  5. Constant force at an angle: • Work (angle between force and displacement). • W = Fd cos 

  6. Power: • The rate at which work is done • P = W/t • Power is measured in watts (joule/second)

  7. PSS • Sketch the problem. • Establish a coordinate system • Draw a vector diagram. • List known and unknowns. • Use the basic equation for work when a constant force is exerted in the same direction as the displacement. Or the equation W = Fd cos which will work in all situations.

  8. Use the work-energy theorem to determine the change in energy of the system. • Use work and time to find power. • Check your answer.

  9. 10.2 Machines • Simple and Compound Machines • The output work can never be greater than the input work • The machine simply aids in the transfer of energy. • Mechanical Advantage • The force you exert on a machine is called the effort force Fe • The force exerted by the machine is called the resistance forceFr

  10. The ratio of resistance force to effort force, is called the mechanical advantage. • Mechanical Advantage • MA = Fr / Fe • This equation can be rewritten using the definition of work • Wo = Wi or • Frdr = Fede • Rearranging this gives • Fr/Fe = de/dr

  11. We know that the mechanical advantage is given by MA = Fr/Fe • For an ideal machine, MA = de/dr • Because this equation is characteristic of an ideal machine, the mechanical advantage is called the Ideal Mechanical Advantage • IMA = de/dr

  12. Efficiency: • The efficiency of a machine is defined as the ratio of output work to input work. • Efficiency (%) = Wo/Wi X 100 • An ideal machine has equal output and input work and the efficiency is 100%. • In terms of mechanical advantage and ideal machine advantage • Efficiency (%) = (Fr/Fe)/(de/dr) X 100 • Efficiency (%) = MA / IMA X 100

  13. Simple machines: • Most simple machines are combinations of one or more of the six simple machines. • They are the lever, pulley, wheel and axel, inclined plane, wedge, and screw. • The IMA of all machines is the ratio of distances moved.

  14. Compound machines: • A compound machine consists of two or more simple machines linked so that the resistance force of one machine becomes the effort force of the second. • The mechanical advantage of a compound machine is the product of the mechanical advantage of the simple machines it is made up of. • MA = MA machine 1 X MA machine 2

More Related