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