Transcript Simple Machines

Simple Machines
A machine is an invention that makes work easier.
Remember that Work = Force x Distance
A simple machine changes:
the strength of a push or a pull force
or the distance of a movement,
to complete a task more easily.
This produces a MECHANICAL ADVANTAGE
The Six Simple Machines
WEDGE
PULLEY
A circular lever that consists of a
grooved wheel rotating about a hub
DID YOU KNOW?
All simple machines
are derived from
either the inclined
plane or the lever.
INCLINED PLANE
Two inclined planes
placed back to back
Any slanting flat surface
SCREW
LEVER
An inclined plane wrapped
around a cylinder
A rigid bar that rotates on
a pivot called a fulcrum
1st Class
Fulcrum in middle
2nd Class
Load in middle
3rd Class
Effort in middle
WHEEL & AXLE
A fixed wheel turning on
a rod through its center
Inclined Plane
An inclined plane or ramp is one of the simplest machines.
An inclined plane is a slanting surface
connecting a lower level to a higher level.
It is easier to push something up a gentle ramp than up a steep one.
Force
Does
is using
decreased
an inclined
but distance
plane is
increased
decrease
so force
work or
stays
distance?
the same
The great blocks of stone that made
the pyramids weren't lifted into
place they were rolled up ramps, or
what we now call inclined planes.
The inclined plane, one of the
simple machines, allows you to raise
great weights with small forces.
Perhaps rollers gave an inventor
the idea for the wheel!
We’ll talk more about wheels later!
Wedge
Wedges are really a kind of inclined plane, but they
are so useful that people give them their own category.
A wedge is two inclined planes aligned back to back
which ends in a sharp edge and separates material.
HowWhen
does athe
wedge
forceincrease
is applied
force?
downward
Hint: Look
onata wedge,
yellow diagram.
it is able to
push outward in two directions.
Levers
A lever is a simple machine made with a rigid arm or a bar.
It has a fixed pivot or fulcrum where it turns.
If you add a push or pull force (effort) on one end of a see-saw,
the other end goes in the opposite direction.
The resisting weight is called the load.
A light person can balance a heavier person on a see-saw.
The lighter person must sit further from the pivot.
What
If shecould
moves
this
thelittle
fulcrum
bearcloser
changeto the
load
in order
she to
will
liftneed
the bigger
less force
bear?
to lift it.
Fulcrum in middle
Load in middle
Three Classes of Levers
Effort in middle
Wheel and Axle
The wheel and axle is generally considered to be a
circular lever, disk-shaped object with a hole in the center. This “wheel”
is attached to a cylindrical rod called an axle. These two parts rotate
together so that force is transferred from one to the other.
The wheels turn around the axle, which is attached to some type of vehicle.
Did You Know?
Gears are wheels with teeth that
can be used to gain force or
speed or change direction.
The invention of the wheel is one of the most
important in the history of man, similar in
importance to the discovery of fire and the
development of writing, and electricity.
Thechanges
force applied
to
What
The
wheel
goes
when
a further
thethe
force
axle
is increased
transfers
distance
with
from
the
axlesame
wheel
toto
wheel?
force
axle?
Pulleys
A pulley is another special kind of wheel.
It has a groove on the outside for a string or rope.
You can raise a flag up a pole with a simple pulley.
When you pull down on the rope, the pulley turns and the flag goes up.
Making work easier
With two pulleys you can
lift twice as much weight
with the same effort. With
more pulleys you can lift
even heavier loads.
Did You Know?
A fixed pulley is fastened to one
spot, and does not move around.
It provides no gain in force,
distance or speed, but it changes
the direction of the force
HowBydoes
adding
a pulley
moreproduce
ropes a
mechanical
to share advantage?
the load
Screws
A screw is an inclined plane wrapped around a cylinder.
It holds things together or lifts materials.
It has a groove called a thread which winds around a spiral shape.
When you turn a wood screw the thread cuts into the wood.
With each turn the screw is pulled into the wood by one thickness of the thread.
You can’t push a screw into wood with your bare hands.
The screw thread multiplies your strength by winding the screw in, a little at a time.
How a screw works
Screws multiply effort. All
the effort to turn them is
concentrated into a small
movement inwards. This
produces a very large force.
HowItisincreases
a screw like
the aforce
wedge?
1. This is an example of:
a) Inclined Plane
b) Pulley
c) Screw
d) Lever
2. Which of the following statement is true?
a) b is the fulcrum, c is the resistance, a is the effort
b) b is the resistance, c is the fulcrum, a is the effort
c)b is the fulcrum, a is the effort, c is the resistance.
d) b is the resistance, a is the fulcrum, c is the effort
3. A simple machine that is actually a kind of inclined plane is a
a) pulley
b) wedge
c) gear
d) balance
4. Decreasing the slant of an inclined plane increases its.
a) effort force
b) Mechanical Advantage
b) Power
d) Work output
5. A screw is an example of a (an)
a) Inclined Plane
b) Wedge
c) ramp
d)pulley
6. A pulley is an example of a (an)
a) Inclined Plane
b) Wheel
c) ramp
d)pulley
7. When you turn the screw it moves forward
(a) with a smaller force
(b) with the same force
(c) by a greater distance
(d) with a greater force
EDHEADS SIMPLE MACHINES