8th Grade Chapter 3 Lesson 5


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8th Grade Chapter 3 Lesson 5

  1. 1. 8 th Grade Chapter 3 Lesson 5 Pgs. 122-128 For Student Use Only
  2. 2. Solids at Work <ul><li>Moving Matter: </li></ul><ul><ul><li>WORK- the movement of an object by force </li></ul></ul><ul><ul><ul><li>WORK= Force x Distance </li></ul></ul></ul><ul><ul><ul><li>Measured in Foot-pounds </li></ul></ul></ul><ul><ul><li>Work in In Metric System: </li></ul></ul><ul><ul><ul><li>One newton-meter (force x distance) is one Joule </li></ul></ul></ul><ul><ul><ul><li>Joule is named after James Prescott Joule </li></ul></ul></ul><ul><ul><ul><ul><li>Joule- metric unit of work and energy </li></ul></ul></ul></ul>
  3. 3. Solids at Work <ul><li>Rate of Work: </li></ul><ul><ul><li>Time= important for mechanical work </li></ul></ul><ul><ul><li>Power= Work/Time </li></ul></ul><ul><ul><ul><li>Work=W/T </li></ul></ul></ul><ul><ul><li>Work is directly related to power- greater work is the same time equals more power </li></ul></ul>
  4. 4. Solids at Work <ul><li>Rate of Work: </li></ul><ul><ul><li>James Watt developed horsepower </li></ul></ul><ul><ul><ul><li>Horsepower: the ability to lift (move) 550 Lbs, 1 foot in 1 sec. </li></ul></ul></ul><ul><ul><ul><ul><li>3 Horsepower meant that it can do the work of three horses in one second </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Average car= 150 hp </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Race car= 500 hp </li></ul></ul></ul></ul>
  5. 5. Solids at Work <ul><li>Simple Machines: </li></ul><ul><ul><li>Helped muscle do work </li></ul></ul><ul><ul><li>Machines- devices for doing work </li></ul></ul><ul><ul><ul><li>Multiply muscle power </li></ul></ul></ul><ul><ul><li>Working Devices: </li></ul></ul><ul><ul><ul><li>Complex mechanical devices- turn potential energy into kinetic energy- use some simple machines </li></ul></ul></ul>
  6. 6. Solids at Work <ul><li>Simple Machines: </li></ul><ul><ul><li>Simple Machines: </li></ul></ul><ul><ul><ul><li>Basic force multiplying machines </li></ul></ul></ul><ul><ul><ul><li>Use many simple machines still today </li></ul></ul></ul><ul><ul><ul><ul><li>Jack to raise a car </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Manual can opener </li></ul></ul></ul></ul><ul><ul><ul><li>Simple Machines help in three ways: </li></ul></ul></ul><ul><ul><ul><ul><li>Multiplying the force </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Changing the direction of force applied </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Multiplying the speed pr distance to force </li></ul></ul></ul></ul>
  7. 7. Solids at Work <ul><li>Mastering Machines: </li></ul><ul><ul><li>Effort: force we apply to a machine </li></ul></ul><ul><ul><li>Resistance: the force the machine helps us overcome (load we are trying to move) </li></ul></ul><ul><ul><ul><li>Mechanical Advantage= Resistance/Effort </li></ul></ul></ul>
  8. 8. Solids at Work <ul><li>Working Law: </li></ul><ul><ul><li>Work input= work put into a machine </li></ul></ul><ul><ul><li>Work output= work received from a machine </li></ul></ul><ul><ul><ul><li>Work output= distance in x force in = distance out x force out </li></ul></ul></ul><ul><ul><li>Law of Work: </li></ul></ul><ul><ul><ul><li>The work put into a machine is equal to the work received from the machine </li></ul></ul></ul><ul><ul><ul><li>Effort force x effort distance = resistance force x resistance distance </li></ul></ul></ul>
  9. 9. Solids at Work <ul><li>Frictional Effects: </li></ul><ul><ul><li>Some effort force goes to overcome friction </li></ul></ul><ul><ul><li>Because of friction: </li></ul></ul><ul><ul><ul><li>Work input is always greater than work output </li></ul></ul></ul><ul><ul><li>Energy is conserved because some energy is lost as heat, sound, etc. </li></ul></ul><ul><ul><ul><li>Work input= work output + work used to overcome friction </li></ul></ul></ul>
  10. 10. Solids at Work <ul><li>Simple Machines: </li></ul><ul><ul><li>6 simple Machines: </li></ul></ul><ul><ul><ul><li>Lever </li></ul></ul></ul><ul><ul><ul><li>Wheel and axle </li></ul></ul></ul><ul><ul><ul><li>Pulley </li></ul></ul></ul><ul><ul><ul><li>Inclined plane </li></ul></ul></ul><ul><ul><ul><li>Wedge </li></ul></ul></ul><ul><ul><ul><li>Screw </li></ul></ul></ul>
  11. 11. Solids at Work <ul><li>Simple Machines </li></ul><ul><ul><li>Lever: </li></ul></ul><ul><ul><ul><li>One of the most useful and versitile </li></ul></ul></ul><ul><ul><ul><li>It can multiply force or speed with or without changing the direction of the effort </li></ul></ul></ul><ul><ul><ul><li>Consists of rigid bar and fulcrum (pivot point) </li></ul></ul></ul><ul><ul><ul><ul><li>Bar is divided into effort arm and resistance arm </li></ul></ul></ul></ul>
  12. 12. Solids at Work <ul><li>Simple Machines </li></ul><ul><ul><li>Lever Parts: Effort arm (where effort is applied) and Resistance arm (where object is moved) </li></ul></ul><ul><ul><li>Types of Levers: </li></ul></ul><ul><ul><ul><li>First class lever- reverses the direction of the effort </li></ul></ul></ul><ul><ul><ul><li>Second class lever- fulcrum is at end and effort is applied at other end- effort force does not change direction </li></ul></ul></ul><ul><ul><ul><li>Third class lever- fulcrum at end and resistance at the other end- force is applied in between- change speed and distance </li></ul></ul></ul>