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# PhysChapter 7

### Simple Machines

Force times Distance (F*D) work
Rate of doing work (W/t) Power
Basic mechanical parts that help us do work simple machines
the force exerted on a simple machine effort
Work out is always __ than work in less than <
a measure of how effectively the work is being used and how much energy is getting converted to other forms that are not being used efficiency
The ___ energy or work produced by a simple machine is always equal to the energy or work put into the machine. Some is just being changed. total
the thing you are moving load or resistance
Resistance Force F_r
the force needed to JUST BEGIN moving the load without the machine Resistance force
the force you actually exert while using the machine Effort force
Effort force F_e
a measure of how the simple machine is multiplying the effort force or motion Mechanical advantage MA
AMA takes into account what? force or energy lost due to friction
Actual mechanical advantage uses what? forces not lengths
simple machines compensate for a smaller effort force by exerting that force over a longer distance Distance Principle
Ideal mechanical advantage uses what? lengths not forces
Effort distance is what? the distance the load is moved with the machine
Resistance distance is what? the distance the load is moved without the machine
a rigid bar that rests on a pivot point called a fulcrum is what? lever
Movement of an object about a central axis or pivot point is what? Rotational Motion
When forces are balanced like on a seesaw when neither side is moving up or down you have what? Rotational Equilibrium
When forces act perpendicularly on a lever rotating around a pivot point it produces this. A moment or torque
Load -- fulcrum --- effort 1st class lever
effort -- load -- fulcrum 2nd class lever
load -- effort -- fulcrum 3rd class lever
examples of 1st class levers see-saw, skull, foot, pry bar
examples of 2nd class levers hand truck, wheel barrow, paper cutter, door hinge
examples of 3rd class levers arm, leg, fingernail clippers, rakes, broom
What does a 1st class lever multiply? effort force _ makes seem easier to do the work
What does a 2nd class lever multiply? same as 1st class, effort force - so use less force to move the resistance
What does a 3rd class lever multiply? effort motion or distance - resistance moves a lot farther than the effort
A modified lever Wheel and axle
modified wheel and axle gears
IMA of gears = number of teeth on the resistance gear / number of teeth on the effort gear
A fixed pulley has an IMA of what? one
A movable pulley has an IMA of what? two
How can you determine the IMA of a pulley system? Count the pulleys
IMA of an inclined plane = length of the incline (le) / height you lift (lr)
A ling thin wedge wrapped around a shaft screw
the number of threads per inch TPI
The greater the pitch on a screw what happens to the mechanical advantage? it decreases
Two or more simple machines working together to make work easier compound machine
examples of a wedge Axe, knife, zipper
Created by: kdcribb