By:
Drew Harris
Simple machines
The basic machines that make up other
machines are called simple machines. There are
six of them. They are lever, pulley, wheel and
axle, inclined plane, screw, and wedge. All these
machines help us move things by changing the
size of the force applied, the direction of the force,
or both at once.
One simple machine is a lever. A lever is made up
of a bar that turns on a fixed point. The fixed point,
or point that doesn’t move, is called the fulcrum.
When you push or pull a lever, you put a force,
called the effort force, on one side of the bar. This
force can be used for any simple machine. Effort
force causes the bar to turn on the fulcrum. The
other end of the bar moves. The resulting force on
that end is what you use to move a load, or do work.
Levers
The kind of lever shown above changes the direction
of the force applied to it. A force down on one side
pushes the other side up. On a seesaw the weight of
a person on the high end pushes that end down.
This lifts the person sitting on the other end.
When the fulcrum of this kind of lever is
not in the middle of the bar, a light weight
on the long side can balance a heavy weight
on the short side.
On a seesaw you can balance a heavier
person if the fulcrum is closer to him or
her. Your smaller weight is on the long side
of the lever. It balances the larger weight
on the other end.
Pry bar
Many hand tools are levers. A pry bar is a lever
that has a long handle and a short end for prying. A
small force on handle becomes a much greater force
on the prying end.
Sewing scissors have long, wedgeshaped blades and short handles. The
fulcrum is the bolt in the middle. A large
movement of the handles causes a small
movement of the blades to close the
bolt.
Fingernail scissors have long handles and
short blades. They make it easier to cut hard
fingernails.
Work
Machines are used to do work. In science, the word
work has a special meaning. Work is done on an object
when a force moves the object through a distance.
The force and motion must be in the same direction.
By this definition, thinking isn’t work. Just holding a book
isn’t doing work. But lifting a book is doing on the book.
Carrying a basketball isn’t doing work on the basketball.
This is because the force holding the ball up and its motion
aren’t in the same direction. Shooting the basketball,
however, is doing work on the basketball.
Measuring Work
Work can be measured and described
mathematically. To find the work done on an
object, multiply the force used to move the
object by the distance the object moves.
Work = force x distance
Examples:
Work = 10 N x 2 m
Work = 20 N – m (Newton-meters)
Pulleys
A pulley is made up of a rope or chain and a
wheel around which the rope fits. When you pull
down on one rope end, the wheel turns and the other
rope end moves up.
A pulley that stays in one place is called a fixed
pulley. Fixed pulleys are often used to raise and
lower something lightweight, such as a flag or a
small sail, while you stay on the ground or the deck.
A fixed pulley is like a lever that has its
fulcrum in the middle. Both the lever and
the pulley change only the direction of the
effort force. They do not change the size of
the effort force.
A different kind of pulley can change the size of
the effort force. This pulley is called a moveable
pulley because it is free to move up and down. One
end of its rope is tied down. The load is hooked to
the pulley. Pulling up on the rope makes both the
pulley and the load rise.
A moveable pulley doesn’t change the direction of
the effort. A pull up on the rope also pulls up on the
land. But a moveable pulley does increase the
resulting force. To lift a load of 50 Newtons, you
need to pull with only a 25-newton force.
As with a lever, you don’t get more work out of a
moveable pulley than you put in it. It doubles your
lifting force, but you pull twice as far. To lift a load 2
meters, you must pull up 4 meters of rope.
Pulley Systems
Pulleys can be put together to make
pulley systems, a form of compound
machines. For example, you can use a fixed
pulley with a moveable pulley. The moveable
pulley increases your force. The fixed pulley
changes the direction of your force.
Adding more moveable pulleys to a
system increases your force even more.
Each moveable pulley you add also increases
the length of rope you must pull to lift a
load.
Pulley System
Wheel and Axle
Wheels and Axles
A wheel and axle is another simple machine that can
make a job easier. A wheel and axle is made up of a
large wheel attached to a smaller wheel or rod.
A doorknob is part of a wheel and axle. The large
round knob turns a smaller axle. The axle is what pulls
in the latch to open the door. Without the large knob, it
would be difficult to turn the axle. The small effort force
you use to turn the knob becomes a large resulting force
put out by the axle.
As with other simple machines, you can’t get more
work out of a wheel and axle than you put in it. Effort
force is made larger. But the distance the outside of the
knob turns is larger than the distance the axle moves.
An inclined plane is a sloping surface,
such as a ramp, used to lift heavy loads
with little effort. The inclined plane does
not move. It works by allowing less force
but over a greater distance.
Screw
A screw is an inclined plane wrapped
around a cylinder. The threads of a screw
form a tiny "ramp" that goes around the
screw. A screw allows you to use less
force, and it changes the direction of the
force.
Wedge
A wedge is an inclined plane that
tapers to a sharp edge A wedge is really
two inclined planes joined back to back. A
wedge changes the direction of the force.
A wedge moves.
Simple Machines
Vocabulary
*simple machine – one of the basic machines that
make
up other machines
*lever – a simple machine made up of a bar that turns
on
a fixed point
*fulcrum – the fixed point, or point that doesn’t move,
on
a lever
*effort force – the force put on one part of a simple
machine, for example, when you push or pull on a
lever
*work – that which is done on an object when a force
moves the object through a distance
*pulley – a simple machine made up of a rope or chain
and a wheel around which the rope or chain fits
*wheel and axle – a simple machine made up of a large
wheel attached to a smaller wheel or rod
*inclined plane – a flat surface with one end higher than
the other
*efficiency – how well a machine changes effort into
useful work
*screw – an inclined plane wrapped around a pole
*wedge – a machine made up of two inclined planes
placed back-to-back
Simple Machines
WHAT IT IS
HOW IT HELPS US
WORK
EXAMPLES
LEVER
A stiff bar that rests on
a support called a
fulcrum
Lifts or moves loads
Shovel, nutcracker,
seesaw,crowbar,elbow,
tweezers,bottle opener
INCLINED PLANE
A slanting surface
connecting a lower
level to a higher level
Things move up or
down it
Slide, stairs, ramp,
escalator, slope
WHEEL AND AXLE
A wheel with a rod,
called an axel, through
its center: both parts
move together
Lifts or moves loads
Car, wagon, doorknob,
pencil sharpener, bike
SCREW
An inclined plane
wrapped around a
pole
Holds things together
or lifts
Screw, jar lid, vise,
bolt, drill, corkscrew
PULLEY
A grooved wheel with
a rope or cable around
it
Moves things up,
down, or across
Curtain rod, tow
truck, mini-blind, flag
pole, crane
WEDGE
An object with at least
one slanting side
ending in a sharp edge
Cuts or spreads an
object apart
Knife, pin, nail, chisel,
ax, snowplow, front of
a boat
VIDEOS
http://www.cleanvideosearch.com/media/action/yt/watch?videoId=L_typfApyVk&name=Six+Simple+Machines%2C
+animated+at+MIT&uploadUsername=pellosborn&hitCount=9303

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th+Bill+Nye&uploadUsername=123peaceplease&hitCount=252781

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
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
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SONGS
 http://www.cleanvideosearch.com/media/action/yt/watch?videoId=l1Fhs8pXGxM&name=Sim
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 http://www.cleanvideosearch.com/media/action/yt/watch?videoId=jiLI6q5wsw0&name=Simp
le+Machines+Song&uploadUsername=parrmr&hitCount=4165
 http://www.cleanvideosearch.com/media/action/yt/watch?videoId=eU_siwyaX84&name=Sim
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 http://www.cleanvideosearch.com/media/action/yt/watch?videoId=yNUgbdsWSm4&name=Si
mple+Machines+Song&uploadUsername=science4us&hitCount=4451
 http://www.cleanvideosearch.com/media/action/yt/watch?videoId=hSI5HjHOiiY&name=Sim
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 http://www.cleanvideosearch.com/media/action/yt/watch?videoId=JfUYdpFmy_I&name=Sim
ple+Machines+%28aka+The+Pulley+Song%29&uploadUsername=songstolearnby&hitCount=4
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