Chapter 11 Section 4 Simple Machines. What is a Simple Machine? Is a machine that takes one force...
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Transcript of Chapter 11 Section 4 Simple Machines. What is a Simple Machine? Is a machine that takes one force...
Chapter 11 Section 4
Simple Machines
What is a Simple Machine? Is a machine that
takes one force and changes its direction, distance, or strength.
A simple machine has few or no moving parts.
Simple machines make work easier.
Introduction
Simple MachinesEffort – force you apply to a machine
Output- the force a machine supplies
Load- the object moved
Simple machines can increase the force we apply.
Simple MachinesWork = force x distanceSimple machines make work easier
because it can increase force needed to move objects or they can decrease the amount of force needed to move the object.
Examples of simple machines are levers, pulleys, wedges, wheel & axle, inclined planes, and screws.
What are Levers ? A lever is a bar that rests on a support
called a fulcrum which lifts or moves loads .
Fulcrum- the pivot point for a lever
Levers multiply effort, distance, and speed.
Levers-First Class In a first class lever
the fulcrum is in the middle and the load and effort is on either side.
The effort and out move in opposite directions.
Think of a see-saw
Levers-Second Class In a second class
lever the fulcrum is at the end, with the load and effort on one side.
Think of a wheelbarrow
Effort ^
Levers-Third Class In a third class lever
the fulcrum is again at the end, but the effort is in the middle
Think of a pair of chop sticks
Wheels and Axles The wheel and axle
are a simple machine.
The axle is a rod that goes through the wheel which allows the wheel to turn to lift or move loads.
Gears are a form of wheels and axles
Pulleys Pulleys are wheels
and axles with a groove around the outside used to raise or lower a load.
A pulley needs a rope, chain or belt around the groove to make it do work.
Inclined Planes An inclined plane is
a slanting surface connecting a lower level to a higher level.
Inclined planes make the work of moving things easier.
Wedges Two inclined
planes joined back to back.
Wedges are used to split things.
Wedges are also used to lift objects.
Screws A screw is an inclined
plane wrapped around a pole which holds things together or lifts materials.
The inclined plane
allows the screw to move itself when rotated.
Compound Machines Compound machines- two or more
simple machines used to move a load.
A compound machine can also use the same simple machine multiple times.
Efficiency- ratio of input energy to output work.
Compound Machine Bulldozer – lever and wedge
Wheelbarrow- levers, wheel and axle,
Scissors- levers and wedges
Hand drill- screw and wheel and axle
Elevator- multiple pulleys