Pulleys
Jenna Loux
Alicia Ferrara
Jess Myers
Nicole Naula
Use the Space Bar to Click
through the Presentation
Before Pulleys
• In Ancient times, such as those
in Egypt and the building of
the Pyramids, to bare a heavy
load brute manual labor was
used to move each stone.
• The slaves in ancient Egypt
would pull heavy stones by
placing it on boards and pulling
ropes that were wrapped
around the stone.
• These stones had to be moved
great distances and as the
pyramid grew taller, it took
more work to get it up the
pyramid. This decreased the
speed of the build as it went
along.
http://www.haitheory.com/
Things to think about…
• It took about 2000 people to
build a Pyramid
• That makes approx. 45
groups of 45
• Which means 315 stones
were moved a day
• Which means 1,890 stones
were moved a week
• Which means it took approx.
1075 weeks to build the
pyramid
• 1075 weeks= 20.6 years
• The Great Pyramid was built
of approx. two million blocks
of stone.
• Each stone weighed approx
2800 kg (2.5 tons)
• It took approx. 45 men to
move a stone to its placement
• Each day 45 men could
move, on average, 7 stones
• With a 12 hour work day, 6
days a week- one team could
move 42 stones to place
http://www.peter-thomson.co.uk/ancients/peoplepyramid.html
Moving Stone
Say you have a 100lb.
Stone to move and
you have to move it
100 feet
To move it only using this
rope your exerting the
force to pull to entire
weight of the stone.
http://science.howstuffworks.com/transport/engines-equipment/pulley.htm
Archimedes
"Give me a lever long enough and a
place to stand, and I will move the
world." -Archimedes 230 BC
http://www.hyperhistory.net/apwh/bios/b2archimedes_p1ab.htm
Archimedes (287-212 BC)
• Was a ancient Greek
mathematician and scientist
• When he was in his teens he
was sent to Alexandria to
study mathematics
• Levers were used early to
move heavy items but at the
age of 27 Archimedes was
able to explain why they
worked
• Explained to the king how
pulleys can be implemented to
move heavy objects.
http://www.school-for-champions.com/biographies/archimedes.htm
First Pulley Thoughts
• If you just use one
pulley to move the
weight you are still
exerting enough force
to life the full 100lbs
• You are still pulling
100 feet of rope to
bring the item up 100
feet.
http://science.howstuffworks.com/transport/engines-equipment/pulley.htm
Two Pulley System
• If you add a second
pulley, two ropes are
holding the item up
instead of one
• This splits the weight
equally between the two
pulleys
• This means you only
have to exert half the
force needed to pull up
the full amount of weight
http://science.howstuffworks.com/transport/engines-equipment/pulley.htm
Force-Distance Tradeoff
When the force needed to pull
something using a pulley is cut in half
the distance of rope that needs to be
pulled will double.
http://science.howstuffworks.com/transport/engines-equipment/pulley.htm
More Pulleys
• The more pulleys you add the
less amount of force you have
to apply to pull the weight up
• With each pulley used it cuts
the force that must be used in
half and the amount of rope
needed doubles
• So a 100lb stone being lifted
100ft with a three pulley
system will need 400ft of rope
but only 25% of the force is
needed
http://science.howstuffworks.com/transport/engines-equipment/pulley.htm
Time and Energy Saver
• Using this method it
saves 25% of the energy
needed to move a stone
with each additional
pulley used, where 1
pulley does not change
the energy needed
• With a 2 pulley system a
pyramid could be built in
15 years, five years less
than before.
http://www.miniscience.com/projects/pulley/
Uses for Pulleys
•
•
•
•
•
•
•
•
Elevators
Lifting car engines
Lifting marine cargo
Cars
Cranes
Building Houses
Tow Trucks
Work-out machines