simple machines sph4c march 2010. history archimedes – 3 rd century bc heron of alexandria –...
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Simple Machines
SPH4C
March 2010
History
• Archimedes – 3rd Century BC
• Heron of Alexandria – 10-75 AD
• Galileo Galilei – 1600 AD
What is a machine?
• Device that allows us to do work with less effort.
• Work is done when a force moves an object in the direction of that force.
Work
• Work is the energy transferred to an object.
• Machines make work easier.
• W is the work done on the object,• F is the magnitude of the force,• Δd is the magnitude of the displacement.
dFW
Machines
• Machines are designed to achieve at least one of five main functions:– Change energy from one form into another– Transfer forces– Change the direction of a force– Change the magnitude of a force– Change distance or speed
Simple Machine Families
• Lever Family– Lever– Pulley– Wheel and axle– Gears
• Inclined Plane Family– Inclined plane– Wedge– Screw
Lever
A lever is a rigid bar that can rotate freely around a fulcrum ( a support around which a lever can rotate).
An effort force, FE, is a force applied to one part of a lever to move a load at another part; the load exerts a load force, FL.
Lever Classes
• First-class– Fulcrum between FE and
FL
• Second-class– FL between FE and fulcrum
• Third-class– FE between FL and fulcrum
Other Levers
Inclined Planes
• An inclined plane is a ramp that increases the load than can be moved by an effort force.
Inclined Planes
• A wedge is a double inclined plane that increases the applied or effort force.
• A screw is an inclined plane wrapped around a central shaft that increases the applied or effort force.
Compound Machines
• A machine made of two or more simple machines.