Work, Power and Simple Machines

1
Work, Power and Simple Machines

• Chapters 13 14

2
Work

• Work is a force exerted over a certain distance
• Work Force x Distance
• Work is measured in Joules (J)

3
Power

• Power is the rate at which work is done
• Power work/time
• Power f x d/time
• Power is measured in Watts (W)

4
Machines

• A machine is an instrument that makes work easier
• Work input is the amount of work put into a
  machine
• Work output is the amount of work done by the
  machine
• Machines make work easier b/c they change either
  the size or the direction of the force put into
  the machine

5
Simple Machines
6
Six Simple Machines

• Inclined Plane
• Wedge
• Screw

• Lever
• Pulley
• Wheel and Axle

7
Inclined Plane

• Inclined plane is a flat slanted surface
• Example- ramps
• A ramp decreases the amount of force you need to
  exert, but increases the distance traveled

8
Wedge

• A wedge is an inclined plane that moves
• Examples door stop, knife, scissors, axe, edges
  of key, zipper, wood splitter

9
Screw

• A screw is an inclined plane wrapped around a
  central cylinder
• Examples wood screw, cork screw, light bulb,
  spark plug, jar lid

10
Lever

• A lever is a rigid bar that is free to move about
  a fixed point.
• Fixed point fulcrum
• Examples crowbar, seesaw, rake, dolly, fishing
  pole, gear shifter, wheelbarrow, hammer

11
Pulley

• A pulley is a rope, belt, or chain wrapped around
  a grooved wheel
• Examples crane, window shade, flag pole,
  sailboat, elevator

12
Wheel and Axle

• A wheel and axle is a machine made up of 2
  circular objects of different sizes.
• Wheel is the larger object
• Axle is the smaller object
• Examples bikes, ferris wheel, door knobs,
  wrench, steering wheel

13
Compound Machine

• A combination of two or more simple machines
  working together.
• Examples washing machine, blender, DVD player,
  sewing machine, vacuum cleaner, toaster.

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Compound Machine