Review of simple Machines

1
Review of simple Machines

• Small things that help us do work in every day
  life

2
What are simple Machines
3
Why Do we call these simple machines?
A simple machine is a mechanical device that
Changes the direction of effort Reduces effort
by changing the magnitude of a force
4
Simple Machines
Force
Load
The lever of a Teeter-totter Changes the
direction of the load.
This lever can reduce the load, but it surely
changes effort direction.

• Change Effort Direction of load. An example is a
  lever or pulley.

5
Reduces effort by changing the Magnitude of the
force
25 lbs of effort 100 lbs of force
50 lbs of effort 100 lbs of force
With this system you can see that there are four
support ropes, so you divide the load by four
Two Support Ropes attached to the load
Mechanical Advantage is created by supporting the
load with more ropes.
6
Levers

• There are three kinds of levers
• First class levers
• Second class levers
• Third class levers

7
Extra Credit

• You will be able to get extra credit for knowing
  the three types of levers and the ability to give
  examples.

8
First Class Levers

• What do First Class Levers do?

1st Class Lever
What you learned from reading.
What you learned from Share-out
Where is the fulcrum?
I learned that the fulcrum has to be between the
load and the effort
Fulcrum is between the effort and load
I learned that the closer the fulcrum is to the
load, the less effort I need to use.
Load
Effort
Fulcrum
9
First Class Levers
Teeter totter
10
Second Class Levers

• What do they do?

What you learned from reading.
What you learned from Share-out
2nd Class Lever
Where is the fulcrum?
I learned that the major difference between a 1st
and 2nd class lever is where the fulcrum is.
Effort
Load
The fulcrum is in front of the load.
Fulcrum
11
Second Class Levers
Wheel Barrow
12
Third Class Levers

• What do they do?

3rd Class Lever
What you learned from reading.
What you learned from Share-out
Where is the fulcrum?
I learned that the major difference between the
different types of levers is where the fulcrum
is.
Load
Effort
Fulcrum is behind the effort.
13
Third Class Levers
Baseball bat or a club
14
Incline Planes Wedges

• Incline planes reduce effort by changing the
  angle of ascenthow steep the slope is.

Advantage is less steps to get to the
top. Disadvantage is each step is more difficult
Steep but a Shorter distancemore difficult
Less steep but twice as long as the steeper
rampLess difficult
Advantage is easier access. Disadvantage is
more steps to get there. (Effort distance is
increased)
15
Advantages and Disadvantages

• Incline planes decrease effort by decreasing the
  angle of assent.
• The trade-off is that the effort distance is
  increased.

You would take fewer steps but each step would
take more effort .
Effort distance
It would be easier to get up this ramp but you
would need to walk further.
Effort distance
16
What you need to know about Wedges

• Wedges change effort direction
• Wedges change effort by increasing or decreasing
  outward force.

Less angle Less Effort needed and less outward
force
Greater the angle more effort and more outward
force
Less outward force
Outward Force
OutwardForce
17
Examples of Wedges Incline Planes
18
What you need to know about Pulleys
Pulleys are good for two reasonstwo
advantages Pulleys change the direction of
effort. Pull down and load goes
up They give us mechanical advantage.
50 lbs of effort
100 lbs of work
19
Single Pulley systems

• Give us change in effort direction and can give
  us mechanical advantage.

Change in Effort Direction
Mechanical advantage
50 lbs of Effort
100 lbs of Load
20
How do We know if there is mechanical advantage?

• We know there is mechanical advantage because
  there is more than one rope supporting the load.

Five Ropes support the load
One Rope Supports the load

100 Lbs of Effort
100lbs of Load
1/5 the effort is needed to lift the load
Does not reduce effort
21
Examples of Pulleys
22
What you need to know about Wheels and Axles.
Wheels reduce friction. Wheels
reduce effort
23
Weels Reduce friction

• By turning on an axle the wheel reduces friction
  and allows loads to move easier.

24
Wheels also reduce effort They increase
leverage by extending the effort farther away
from the fulcrum
Fulcrum
Effort