Simple Machines
Lesson 19
What You Will Learn
✹ How
can you make doing a job, such as
lifting a heavy box, easier?
✹ In this lesson, you will investigating a number
of simple machines and learn how they make
work easier.
✹ You will identify the six simple machines.
✹ You will also determine the amount of work
needed to do work using the simple
machines.
Work and Force
✹ https://gizmodo.com/a-brief-history-of-
physics-1147115801
✹ In science, work is defined as a force
moving an object over a distance.
✹ A force is a push or pull.
✹ When you push a shopping cart, kick a
ball, or lift a heavy box, you are doing
work.
Work
✹ Work
is done only if an object moves.
✹ If you hold a heavy object steady above
the ground, you are not doing work,
even though your arms may get tired.
✹ If you lift the box a fraction of an inch,
you are doing work.
The 6 Simple Machines-
a simple machine is a device that makes work easier and that has few
or no moving parts.
Inclined Plane
Screw
Pulley
Lever
Wedge
Wheel and Axle
Simple Machines
✹ Simple
machines make work easier by
changing the size or direction or both of
the force used to do the work.
✹ A simple machine does not allow you to
do less work.
✹ It just makes the work easier for you to do.
✹ The equation for work is
Work=force X distance
✹ W=Fd
✹
W=Fd
✹ In
this equation, work will stay the same
while force is reduced as distance
increases.
✹ A simple machine can decrease the
force needed to move an object, but
force must be applied over a greater
distance.
Definitions:
Energy: Ability to do work
Work: Force x Distance
Force: A Push or a Pull
Inclined Plane
Inclined Planes
✹
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An inclined plane is a
flat surface that is
higher on one end
Inclined planes make
the work of moving
things easier
A ramp is an
example of an
inclined plane
Inclined Plane
✹
✹
It is easier to push an
object up a ramp than it
is to lift the same object
straight up to the same
height.
Increasing the distance
decreases the force
needed to so the same
amount of work.
Screw
• When a screw is turned, a small force is applied over
the long distance of the screw’s threads.
• This makes the work of moving the screw into a board
easier.
• This is similar to driving around a mountain to get to the
top as opposed to driving straight up.
Wedges
✹
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Two inclined planes
joined back to back.
Wedges are used to
split things.
A wedge changes the
direction of a force.
Wedges transfer force
in one direction into a
force in two directions.
Levers
A lever is a simple machine made up of a
bar that pivots at a fixed point called a
fulcrum.
✹ The force applied to a lever is called the
effort.
✹ The object moved is the load.
✹ A lever allows a person to move a large
load with relatively little force.
✹ As force is applied to one end, the other
end moves in the opposite direction.
✹
Levers
.
✹
Common examples of levers
include crowbars, scissors,
pliers, tin snips, and seesaws.
Levers
✹ Other
examples of
levers include
wheel barrows,
doors, and bottle
openers.
Pulleys
✹
✹
✹
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A pulley is a rope
wrapped around a wheel.
A pulley needs a rope,
chain or belt around a
groove to make it do
work.
A load is attached to one
end of the rope.
A force is applied to the
other end.
WHEEL AND AXLE
✹
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A wheel and axle consists
of two connected cylindershaped objects with
different diameters.
The wheel is always larger
than the axle.
When an applied force
turns the wheel, the axle
turns too.
The axle moves a shorter
distance than the wheel, so
the axle turns with greater
force.
A doorknob and a
screwdriver are examples
of a wheel and axle.
Review
✹
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Name the six simple machines…
Find three examples of each.
How does each one make work easier?
Sally has an ax that she uses to chop wood.
The metal part chops through the wood,
pushing it apart into two smaller sections.
Which simple machine is found on the head of
the ax?
A wedge
✹ Sally
and Sue are across the street on
the seesaw. The center of the seesaw is
used to balance the board with the
seats. The two girls can easily move up
and down without much force.
✹ The seesaw is an example of which
simple machine?
✹ A lever
✹ The
cap on Sam’s water bottle has a
spiral shape. When he places it on the
bottle and twists, the cap pulls itself
toward the bottle.
✹ The bottle cap is an example of which
simple machine?
✹ A screw
✹ When
you turn the large knob on a door,
a rod on the inside releases a latch that
holds the door closed. It would be
difficult to turn the rod if the knob wasn't
attached to it.
✹ The door knob and rod make up which
simple machine?
✹ A wheel and axle.
✹ A wheel
with a rope is used to hoist a
flag up to the top of a tall flagpole. The
simple machine can also be used to
help lift heavy objects with less force.
✹ The wheel and rope make up which
simple machine?
✹ A pully