1 / 17

Machines

Machines. Science Chapter 5 Section 2. Machine. Definition: A device that makes work easier Does NOT decrease work! Makes work easier by: Changing direction of force needed to do work Changing distance force is applied (also changes amount of force). Change direction of Force.

oral
Download Presentation

Machines

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. Machines Science Chapter 5 Section 2

  2. Machine • Definition: A device that makes work easier • Does NOT decrease work! • Makes work easier by: • Changing direction of force needed to do work • Changing distance force is applied (also changes amount of force)

  3. Change direction of Force

  4. Change distance force is applied

  5. Machine • Two forces are involved in using machine: • Effort force (FE): the force applied to the machine • Resistance force (FR): the force the machine uses on the object we want to move • FR is also sometimes called load force

  6. Machine • Two kinds of work calculated when using the machine: • Input Work: Work done by you to use the machine (Win) • Output Work: Work done by the machine to move the object (Wout)

  7. Remember! • Work is done by transferring energy! • We cannot create or destroy energy! • Some energy becomes non-useful any time work is done! • Therefore, Wout is always less than Win!

  8. Mechanical Advantage • MA: the amount a machine helps you do the work • Calculated in two ways: • Ideal Mechanical Advantage • Actual Mechanical Advantage

  9. Ideal Mechanical Advantage • IMA = deffort / dresistance • This is theoretical MA • Does not take “loss” of energy into account

  10. Actual Mechanical Advantage • AMA = Fresistance / Feffort • “Real World” mechanical advantage • Takes friction and “loss” of energy into account

  11. Example • Grok uses a ramp to push a 1500 N rock up to his cave from the valley below. The vertical distance from the valley floor to the cave is 50 m. The ramp is 150 m long, and Grok must push with a force of 500 N to move the rock up the ramp. What is the IMA of the ramp?

  12. Grok’s Rock Example Continued • What we know: • Feffort=500 N • Fresistance=1500 N • deffort=150 m • dresistance=50 m • Equation • IMA = deffort / dresistance

  13. Grok’s Rock Example • Substitute numbers in: • IMA = 150m/50m • Solve: • IMA = 3 • Check for units! • Whoops, no units for MA!

  14. Efficiency! • Efficiency is another measure of how well the machine works • Efficiency compares the work you get out to the work you put in • Efficiency = Wout/Win x 100 (given as percent) • Efficiency is ALWAYS less than 100%!

More Related