Simple Machines Review - Mr. Finke's Science Class€¦ · Complex Machines •Combining two or...
Transcript of Simple Machines Review - Mr. Finke's Science Class€¦ · Complex Machines •Combining two or...
Simple Machines
Introduction to
What are they?
Simple machines are machines
with few or no moving parts
that are used to make work easier
Types of Simple Machines
Wedge
Wheel and Axle
Lever
Inclined Plane
Screw
Pulley
Wedge
• Pushes materials apart, cuts things
• Examples: axe, doorstop, chisel,
nail, saw, jackhammer, bulldozer,
snow plow, horse plow, zipper,
scissors, airplane wing, knife, fork,
bow of a boat or ship
The Wedge
• A wedge is used to
split, tighten, or secure
a hold.
• A wedge is usually a
triangle shape with a
sharp point.
• If you apply force at one
end, the wedge will go
between something, in
this case an ax splits a
piece of wood.
Where can we find wedges?
• Wedges that split:
• Your teeth!
• Every time you bite
into something, you
are using a wedge.
• Wedges that cut:
• A saw!
• A knife!
• Wedges that tighten:
• A doorstop to keep
the door open.
• Wedges that hold
things together:
• A nail holds wood to a
wall or other wood.
Wheel and Axle
• Makes it easy to move things by rolling them,
and reducing friction
• Examples: car, bicycle, office chair,
wheel barrow, shopping cart,
hand truck, roller skates
The Wheel and Axle
• Two or more wheels
are connected by an
axle.
• The wheel turns with
or around the axle.
• This car wheel has a
big axle that it
rotates around when
the car moves.
Why do we need wheels?
• Wheels help us move heavy objects.
• They roll easily.
• Did you know a doorknob is really two
wheels connected by an axle? You can’t
see the axle because it’s inside the
wheels, but it’s there!
• If there wasn’t an axle, the doorknob
wouldn’t turn!
Another kind of wheel is called a
gear! • A gear is a wheel with teeth.
• The teeth fit in between each other and
turn.
• When one gear turns, its teeth push
against the teeth of the other gear and
they both turn.
• There are gears on your bike, on a can
opener and on an egg beater.
Lever
• Makes lifting weight easier by using a fulcrum
to redirect force over a longer distance
• Examples: see-saw, dump truck, broom, crane
arm, hammer claw, crow bar, fishing pole,
screwdriver, bottle opener
Levers
• There are three
parts to a lever:
• Load
• Force
• Fulcrum: support or
balance
A seesaw is a lever
• Let’s pretend you are
riding a seesaw with your
friend.
• The center support is the
fulcrum, which does not
move.
• The load is your friend
sitting on one end.
• You exert the force at the
other end trying to lift
your friend off the ground.
• When you push down on your
seat, (the force) you can lift
your friend (the load) while the
fulcrum acts as the pivot point,
making the seesaw go up and
down.
• It’s easy to lift your friend this
way instead of just picking her
or him up by yourself!
Inclined Plane
• Makes it easier to move objects upward,
but you have to go further horizontally
• Examples: highway or sidewalk ramp,
stairs, inclined conveyor belts, switchback
roads or trails
The Inclined Plane
• It is a slanted surface
or ramp.
• It makes moving
objects easier.
• Roads are also
inclined planes.
Instead of going
straight up, like this:
roads go up at small
angles, like the
picture.
Screw
• Turns rotation into lengthwise movement
• Takes many twists to go a short distance
• Holds things together
• Examples: screws, bolts, clamps, jar lids,
car jack, spinning stools, spiral staircases
The Screw
• The three parts to a
screw:
• Head
• Shaft
• Tip
• The head is the part that
you exert a force on.
• The shaft has ridges,
called threads that wind
around the screw. If it
doesn’t have the threads,
it is probably just a nail.
• The tip is sharp.
How to use a screw:
• Fasten two things together
• When you turn it, the threads cut a groove
in the material, making a hole. The groove
holds the screw tightly in place.
• To remove the screw you turn it the
opposite way, you can’t just pull it out.
Pulley
• Makes lifting things with a rope easier
by redirecting force and the addition
of additional pulleys
• Examples: flag pole, elevator, sails,
fishing nets, clothes lines, cranes,
window shades and blinds, rock
climbing gear
Pulleys
• Lifting a bucket full of water
is a lot of work!
• A pulley is a wheel with a
rope running over it. The
wheel has a groove, called a
sheave, and it keeps the
rope from slipping off the
wheel.
• Remember, since there is a
wheel in a pulley there also
has to be an axle!
• These two men are using a
pulley to help them lift their
heavy bucket.
Why Use Simple Machines?
For the mechanical advantage…
• Making something easier to do,
but it takes a little longer to do it
• For example, going up a longer flight
of stairs instead of going straight up a
ladder
Complex Machines
• Combining two or more simple machines
to work together
• Examples:
– Car jack combines wedge and screw
– Crane or tow truck combines lever and pulley
– Wheel barrow combines wheel and axle
with a lever
Summary
Wedge Pushes material apart, cuts
Wheel
and Axle
Makes it easy to move things
by rolling them, and reducing friction
Lever Helps lift heavy weights
using longer distances
Inclined
Plane
Makes it easier to move objects upward;
a longer path, but easier lifting
Screw Turns rotation into lengthwise movement
Pulley
Makes lifting heavy weights easier
by redirecting force
Compound Machines
• Compound machines consist of two or
more simple machines put together.
• Most devices are compound machines.
• They can do more difficult jobs because
their mechanical advantage is greater.
Name the Simple Machines
Present in Each Compound Machine
Compound Machines
COMPOUND MACHINES
• A compound
machine is a
combination of
two or more
simple
machines that
operate
together.
COMPOUND MACHINES
• Many familiar
compound machines,
such as a car, a
washing machine, or a
clock, are
combinations of
hundreds or thousands
of simple machines.
Compound Machine
Corkscrew
• Inclined Plane
• Wedge
• Screw
• Lever
• Wheel and Axle
Compound Machine
Jack
• Inclined Plane
• Wedge
• Screw
• Lever
A Wedge in a Compound Machine:
Stapler
• Staples are
wedges: they cut
through paper
because their
ends are pointed
in a wedge shape.
• Simple machines
in a stapler:
– Wedge
– Lever
A Wedge in a Compound Machine:
Scissors
• The cutting edge
of scissors is a
wedge.
• Simple machines
in a pair of scissors:
– Wedge
– Lever