Chapter 8
description
Transcript of Chapter 8
![Page 1: Chapter 8](https://reader036.fdocuments.in/reader036/viewer/2022070419/56815a9a550346895dc8187b/html5/thumbnails/1.jpg)
Chapter 8Chapter 8Work and Machines
![Page 2: Chapter 8](https://reader036.fdocuments.in/reader036/viewer/2022070419/56815a9a550346895dc8187b/html5/thumbnails/2.jpg)
Lesson 1: WorkLesson 1: WorkWork when something moves because of a force being applied
Work = force x distanceLabel is newton-meter or joule
![Page 3: Chapter 8](https://reader036.fdocuments.in/reader036/viewer/2022070419/56815a9a550346895dc8187b/html5/thumbnails/3.jpg)
Work formulaWork formula
w
f d
![Page 4: Chapter 8](https://reader036.fdocuments.in/reader036/viewer/2022070419/56815a9a550346895dc8187b/html5/thumbnails/4.jpg)
Lesson 2: EnergyLesson 2: EnergyEnergy ability to do workThere are 2 kinds of energy◦Kinetic energy in motion◦KE = ½ mv²◦Potential stored energy◦PE = mghgravity = 9.8 m/s²
![Page 5: Chapter 8](https://reader036.fdocuments.in/reader036/viewer/2022070419/56815a9a550346895dc8187b/html5/thumbnails/5.jpg)
6 Forms of Energy6 Forms of EnergyChemical energy stored in the bonds btw. atoms
Heat energy moving particles in matter
Mechanical energy in moving objects
![Page 6: Chapter 8](https://reader036.fdocuments.in/reader036/viewer/2022070419/56815a9a550346895dc8187b/html5/thumbnails/6.jpg)
6 Forms of Energy 6 Forms of Energy cont.cont.
Nuclear energy stored in the nucleus of atoms
Radiant energy light energy
Electrical energy causes electrons to move
![Page 7: Chapter 8](https://reader036.fdocuments.in/reader036/viewer/2022070419/56815a9a550346895dc8187b/html5/thumbnails/7.jpg)
Energy can be converted from one form to another
Generator device used to convert mechanical energy to electrical energy
Law of conservation of energy energy cannot be created nor destroyed
![Page 8: Chapter 8](https://reader036.fdocuments.in/reader036/viewer/2022070419/56815a9a550346895dc8187b/html5/thumbnails/8.jpg)
Lesson 3: LeversLesson 3: LeversSimple machines tool that makes it easier or possible to do work
Lever bar that is free to turn around a fixed point
Fulcrum fixed point around a lever turns
![Page 9: Chapter 8](https://reader036.fdocuments.in/reader036/viewer/2022070419/56815a9a550346895dc8187b/html5/thumbnails/9.jpg)
LeversLevers cont. cont.
Effort force (FE force applied to a machine by the user
Resistance force (FR) force applied to the machine by the object to be moved
![Page 10: Chapter 8](https://reader036.fdocuments.in/reader036/viewer/2022070419/56815a9a550346895dc8187b/html5/thumbnails/10.jpg)
3 Classes of Levers3 Classes of LeversBased on the position of the resistance, fulcrum, & effort
First-class lever fulcrum is btw effort & resistance
Changes direction of force & can increase force
![Page 11: Chapter 8](https://reader036.fdocuments.in/reader036/viewer/2022070419/56815a9a550346895dc8187b/html5/thumbnails/11.jpg)
Examples of class 1 levers include:
Teeter-totter Scissors Pair of pliers
![Page 12: Chapter 8](https://reader036.fdocuments.in/reader036/viewer/2022070419/56815a9a550346895dc8187b/html5/thumbnails/12.jpg)
Second-class lever resistance is btw effort and fulcrum
Always increases forceDo not change direction
![Page 13: Chapter 8](https://reader036.fdocuments.in/reader036/viewer/2022070419/56815a9a550346895dc8187b/html5/thumbnails/13.jpg)
Examples of class 2 levers include:
Wheelbarrow Crowbar Nut cracker
![Page 14: Chapter 8](https://reader036.fdocuments.in/reader036/viewer/2022070419/56815a9a550346895dc8187b/html5/thumbnails/14.jpg)
Third-class levers effort is btw resistance & fulcrum
Increases distance which cause resistance to move further or faster
![Page 15: Chapter 8](https://reader036.fdocuments.in/reader036/viewer/2022070419/56815a9a550346895dc8187b/html5/thumbnails/15.jpg)
Examples of class 3 levers include:
Tweezers Stapler
Mousetrap Broom Hockey stick
![Page 16: Chapter 8](https://reader036.fdocuments.in/reader036/viewer/2022070419/56815a9a550346895dc8187b/html5/thumbnails/16.jpg)
Efficiency Efficiency A simple machine cannot do more work than the person using it
Machines increase or change the direction of force
If less effort is needed, more distance is needed also
![Page 17: Chapter 8](https://reader036.fdocuments.in/reader036/viewer/2022070419/56815a9a550346895dc8187b/html5/thumbnails/17.jpg)
Effort distance & resistance Effort distance & resistance distancedistance
Effort distance (dE) the distance the effort moves
Resistance distance (dR) the distance the resistance moves
Effort distance is greater than resistance distance
![Page 18: Chapter 8](https://reader036.fdocuments.in/reader036/viewer/2022070419/56815a9a550346895dc8187b/html5/thumbnails/18.jpg)
Work Input & Work Output Work Input & Work Output Work input work put into a machine by the user◦Work input = FE x dE
Work output work done by a machine against the resistance◦Work output = FR x dR
![Page 19: Chapter 8](https://reader036.fdocuments.in/reader036/viewer/2022070419/56815a9a550346895dc8187b/html5/thumbnails/19.jpg)
EfficiencyEfficiencyEfficiency =
work output work input x 100
FR x dR
FE x dE x 100
![Page 20: Chapter 8](https://reader036.fdocuments.in/reader036/viewer/2022070419/56815a9a550346895dc8187b/html5/thumbnails/20.jpg)
Lesson 4: Mechanical Lesson 4: Mechanical advantageadvantageMechanical advantage
number of times a machine multiplies its effort force◦Mechanical advantage =
resistance forceeffort force
◦MA = FR
FE
![Page 21: Chapter 8](https://reader036.fdocuments.in/reader036/viewer/2022070419/56815a9a550346895dc8187b/html5/thumbnails/21.jpg)
Effort Arm & Resistance ArmEffort arm distance btw the fulcrum & effort force
Resistance arm distance btw the fulcrum & resistance force◦MA = effort arm
resistance arm
![Page 22: Chapter 8](https://reader036.fdocuments.in/reader036/viewer/2022070419/56815a9a550346895dc8187b/html5/thumbnails/22.jpg)
Lesson 5: Other simple Lesson 5: Other simple machinesmachines
Pulley wheel w/ a rope, chain, or belt around it
A single pulley changes direction, not force; ma = 1
Fixed pulley attached at topMovable pulley entire pulley & object attached will rise
![Page 23: Chapter 8](https://reader036.fdocuments.in/reader036/viewer/2022070419/56815a9a550346895dc8187b/html5/thumbnails/23.jpg)
Pulley Pulley cont.cont.
MA of a pulley = number of ropes that pull upward
The easier to lift an object, the more distance you pull on the rope
![Page 24: Chapter 8](https://reader036.fdocuments.in/reader036/viewer/2022070419/56815a9a550346895dc8187b/html5/thumbnails/24.jpg)
Inclined PlaneInclined PlaneInclined plane made of a ramp used to lift an object
MA = length of ramp height of ramp
◦Gradual slant = greater MA, but greater distance
◦Steeper slant = less MA, but shorter distance
![Page 25: Chapter 8](https://reader036.fdocuments.in/reader036/viewer/2022070419/56815a9a550346895dc8187b/html5/thumbnails/25.jpg)
ScrewScrewScrew inclined plane wrapped around a nail
MA depends on distance btw threads◦Smaller distance = more MA
![Page 26: Chapter 8](https://reader036.fdocuments.in/reader036/viewer/2022070419/56815a9a550346895dc8187b/html5/thumbnails/26.jpg)
Wedge Wedge Wedge 2 inclined planes placed back to back; inclined plane that moves when used
Thick at one end, thinner at the other◦Thinner, more gradual wedge = greater MA
![Page 27: Chapter 8](https://reader036.fdocuments.in/reader036/viewer/2022070419/56815a9a550346895dc8187b/html5/thumbnails/27.jpg)
Wheel & AxleWheel & AxleWheel & axle wheel attached to a shaft
Increases the force you apply to the wheel
MA depends on the size of the wheel & thickness of axle