Download Slide 1 - Norridge District 80

Chapter 4: Work & Simple
Machines
Review PowerPoint
Describe the six simple machines.
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Inclined plane: flat sloped surface
Wedge: Moveable inclined plane
Screw: Inclined plane wrapped around a post
Lever: Rod or plank that pivots
Wheel & axle: Two circular object that are
attached and rotate together
Pulley: Grooved wheel with a rope or chain
wrapped around it
How are the simple machines
useful?
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Inclined plane: decreases force, increases
distance
Wedge: MA increases as it becomes longer
and thinner
Screw: Changes direction of input force
Lever: MA changes based on location of
fulcrum
Wheel & axle: MA is usually greater than one
Pulley: Changes direction of force
Give an example of each simple
machine.
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Inclined plane: Ramp
Wedge: Axe
Screw: Top of water bottle
Lever: Baseball bat
Wheel & axle: Doorknob
Pulley: Flagpole
What is power?
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Rate at which work is done
What is a compound machine?
Give an example.
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Two or more simple machines that work
together
Lawnmower is made up of a lever,
wheel and axle, and a wedge.
What is mechanical advantage?
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MA is the amount by which a machine
multiplies an input force.
What is efficiency?
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The work output of a machine divided
by the work input.
Contrast input and output force.
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Input force is what you apply to a
simple machine.
Output force is what you overcome
when using a simple machine.
What is work?
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Work depends on the force applied to
the object and the distance the object is
moved.
Why is it important for tires on a car
be inflated the proper amount?
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Low air increases the friction between
the tires and the road. This reduces the
efficiency.
How is oil helpful between
surfaces?
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Oil fills the gaps between surfaces and
prevents many spots on the surfaces
from coming in contact, reducing the
force of friction.
Know how to calculate work.
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Work = Force x distance
Measured in Joules
Know how to calculate power.
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Power = Work/Time
Measure in Watts
Know how to calculate
Mechanical Advantage.
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MA = Output force/Input force