Work and Simple Machines

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Work and Simple Machines
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What is work?

• Work occurs when a force causes an object to move
  in the direction of the force.
• If there is no movement, there is no work
• Movement and force must be in the same direction.

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A mouse pushing a piece of cheese across the
floor is doing work. Both the force and motion
are in the same direction.
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Which is work?

• A scientist delivers a speech to an audience of
  his peers.
• A body builder lifts 350 pounds above his head.
• A mother carries her baby from room to room.
• A father pushes a baby in a carriage.

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Which is work?

• A scientist delivers a speech to an audience of
  his peers.
• A body builder lifts 350 pounds above his head.
• A mother carries her baby from room to room.
• A father pushes a baby in a carriage.

No
Yes
No
Yes
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Formula for work

• Work Force x Distance
• Unit of force is newtons (N)
• Unit of distance is meters (m)
• Unit of work is a joule (j)

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Simple Machines

• Ancient people invented simple machines that
  would help them overcome forces and allowed them
  to make work easier.

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Simple Machines

• The six simple machines are
• Lever
• Wheel and Axle
• Pulley
• Inclined Plane
• Wedge
• Screw

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Simple Machines

• A machine is something that helps make work
  easier by changing the size or direction of a
  force.
• Using a machine does not mean that you do less
  work.

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The Leveris a stiff bar that rests on a support
called a fulcrum which lifts or moves loads.

• Examples

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The Lever

• Every Lever has three (3) parts
• 1. Load - What you are trying to move or lift.
• 2. Effort Force or Output Force - The work done
  on the Lever.
• 3. Fulcrum A fixed pivot point.

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Wheel and Axle

• A wheel with a rod, called an axle, through its
  center lifts or moves loads
• Examples of wheel and axles wagon, toy car,
  Ferris wheels, and doorknobs.

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The Pulley

• A pulley is a simple machine that uses grooved
  wheels and a rope to raise, lower or move a load
• A pulley may be fixed, moveable, or used in
  combination.

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Inclined Plane

• An inclined plane is a slanting surface
  connecting a lower level to a higher level. (
  Ex. a ramp.)

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Wedge

• A wedge is an object with at least one slanting
  side ending in a sharp edge, which cuts material
  apart.

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Screw

• A screw is an inclined plane that is wrapped
  around a cylinder.

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Compound Machines

• A machine that is made of two or more simple
  machines.