Welcome to a world full of machines

1
Welcome to a world full of machines!

• There are machines all around us!
• Ask yourself now what kinds of machines you saw
  on your way to school today.

2
Why do we need simple machines?

• Work means that we are exerting force and moving
  something. The 6 simple machines make our work
  easier. They make work easier not because they
  let us do less work nor does it increase the
  amount of energy put it, but it does change the
  direction of the force or increase the force at
  the cost of distance.

3
The 6 Simple Machines

• All machines are made up of some of the 6 simple
  machines. They are
• Wheel and axle
• Pulley
• Lever
• Wedge
• Screw
• Inclined Plane

4
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.

5
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 cant see the axle
  because its inside the wheels, but its there!
• If there wasnt an axle, the doorknob wouldnt
  turn!

6
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.

7
Levers

• There are three parts to a lever
• Load
• Force
• Fulcrum support or balance

8
A seesaw is a lever

• Lets 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.
• Its easy to lift your friend this way instead of
  just picking her or him up by yourself!

9
Types of levers (The type of lever is determined
by where the effort and load are in relation to
the fulcrum)

• 1st class lever
• The fulcrum is between
• the effort and the load.
• Results  Changes the direction of the force. 
  Could be either a mechanical disadvantage or a
  mechanical advantage.
• Examples

10
2nd class levers

• The effort and load are on the same side of the
  fulcrum but the effort is farther out.
• Results  The effort is always less than the
  load. (has a mechanical advantage) That means you
  always get more force out than you put in.
• Examples wheel barrow, bottle opener, nut
  cracker

11
3rd class lever

• The effort and load are on the same side of the
  fulcrum but the effort is closer in.
• Results  The effort is always more than the
  load. (has a mechanical disadvantage)  That means
  you always get less force out than you put in.
• Examples broom, hammer, fishing rod

12
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!
• This machine helps us do work b/c it changes the
  direction of the force being applied making it
  easier for use to provide a force.

13
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.

14
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.

15
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 doesnt have the threads,
  it is probably just a nail.
• The tip is sharp to increase pressure for easier
  insertion.

16
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 cant just pull it out.
• It makes work easier because it increases the
  distance so you can use less force.

17
The Inclined Plane

• It is a slanted surface or ramp.
• It makes moving objects easier because of
  increased distanceless force needed.
• Roads are also inclined planes. Instead of going
  straight up, like this roads go up at small
  angles, like the picture.

18
The 6 Simple Machines
Lever
Inclined Plane
Pulley
Wheel and Axle
Wedge
Screw
19
Energy conversion and machines

• Regardless of function or energy source, the
  useful energy output of any machine is always
  less than the total energy input.
• This is related to the overall efficiency of a
  machine. If a machine is high in efficiency,
  it means that much of the work input is changed
  to useful work output. In energy terms, most of
  the energy you put into the machine transformed
  into useful forms of energy that helped you do
  work instead of being turned into wasted forms
  that are useless (most often this is HEAT or
  THERMAL energy).
• NO machine on earth is 100 efficient due to
  friction and energy conversion into HEAT (Thermal
  Energy).

20
Calculating Efficiency ()

• Formula Work output/work input X 100.
• If I had a car engine that put 400 J worth of
  work into moving my car, but only got out 80 J
  worth of work out of my engine, what would be the
  overall efficiency of my car engine?
• 20 efficiency- most automobiles are
  approximately this efficient.
• Now think about why it is not such a good idea to
  drive a gas guzzler like an SUV.