# Ch 13 part 2 Simple Machines

```Ch 13 part 2 Simple Machines
Pages 426-431
http://dai.ly/x3cvmov
http://www.dailymotion.com/video/x3cvmov `
A. Machines and work
Work is done when force causes an
object to move
Machine= device that changes the
direction or amount of force needed to
do work
1.
2.
◦
3.
DO NOT reduce work= just make it easier to
do the work
The amount of force decreases BUT the
force must be applied over a greater
distance
B. Simple Machine #1 Pulley
https://youtu.be/aMx7nIIH9ik?t=47s
1. Pulley= consists of a rope or cable that runs through a
grooved wheel
2. Simple pulley makes work easier by changing the
direction of force needed to do work
3. Block and tackle= system of pulleys that make it easier
to lift very heavy objects

Block= pulley and the tackle is the rope through the pulleys
C. Simple machines #2 Wheel and Axle
https://youtu.be/P7xu9O0miEc?t=47s
Wheel and axle= made of a circular
object and a shaft
1.
◦
◦
Reduces the amount of force needed to do
work
Door knob, steering wheel,
Stop and Think
What is a machine?
1.
◦
A device that changes the direction or the amount of
force needed to do work
How are a pulley and a wheel and axle alike and
different?
2.
◦ Both have wheels
◦ A pulley has a rope &amp; it changes the direction of the force
◦ A wheel&amp; axle has a shaft &amp; it reduces the amount of
force needed to do work
When a wheel and axle as well as a pulley make it
easier to raise a bucket of water from a well, has
the work changed?
3.
◦
The amount of work has not changed b/c the amount
of work has stayed the same- the machine made it
easier to do the work
D. Simple machine #3 Lever
https://youtu.be/OdM2jWg2uEE?t=46s
Lever= type of simple machine in which a
stiff bar rotates around a fixed point called
the fulcrum
1.
◦
◦
A see-saw is a fulcrum that changes the amount
of force needed to move an object
Further away the fulcrum is from the person the
easier the lever is to use
E. Simple Machine #4 Inclined Plane
https://youtu.be/E_ErI0QjNos?t=49s
Inclined plane= simple machine consists of a
flat surface with one end higher than the other
1.
◦
Doorstops &amp; axes are inclined planes
Screw= smooth metal rod with tin inclined
planes wrapped around it
2.
◦
Archimedes invented the screw in ancient Egypt (3rd
century B.C) to move water from the ground
3.
Wedge= inclined plane used to separate
objects
Stop and Think
What common playground equipment is a
lever? Which is an inclined plane?
1.
◦
◦
See-saw (teeter totter)
Slide
How is the movement of rolling a weight
up an inclined plane different from climbing
stairs?
2.
◦
Climbing stairs requires more force
What kind of simple machine is a bottle
opener?
3.
◦
A lever
F. Complex Machines
https://youtu.be/k_aTRL2Ircw
Complex machine uses 2 or more simple machines
2. Many use electricity, magnetism, gravity, burning fuel, or
human force to use
1.
Stop and Think
What is a complex machine?
1.
◦
Machine that uses 2 or more simple machines
How are the pedals of the go cart similar
to the rudder of a sailboat?
2.
◦
Both use levers
What parts of a complex machine work
together to make the complex machine
operate?
3.
◦
All of the simple machines work together to
make the complex machine operate!
```