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Unit 4: Energy (Part 1) Page 12
In a second-class lever, the load is close to the Syracuse walls,
between the fulcrum and the Archimedes’ crane would grab
effort. them and turn them over! Go
science!)
The third-class lever has the effort
between the load and the fulcrum. Mechanical Advantage
The Pulley There’s one more thing I’d like to
add here, is the concept of
When we mechanical advantage. The
played with definition of mechanical advantage
levers we is that it is the factor by which a
could see that, mechanism multiplies the force put
by using a into it. The whole idea behind
simple simple machines is that they give
machine, we you an advantage. In other words,
were able to they help you do things more
use less force to move a heavy easily.
object than we would have had to
use if we didn’t use a simple The nice thing about pulleys is that
machine. We also saw that with it is very easy to see the
that lessening of force came an mechanical advantage. You noticed
increase in distance. when you used one pulley that it
took about the same amount of
Obviously, you can only make a effort to lift the load. That would be
lever so long. After a while it gets a mechanical advantage of one.
kind of ridiculous. Imagine lifting a However, when you used two
concrete block or a car with a pulleys, half the effort lifted the
lever. That’s a big lever and you load. You only had to pull half as
probably still wouldn’t be able to hard to lift the load. The pulleys
lift the car very high. This is where doubled your strength. In this
pulleys come in. case, the mechanical advantage is
two.
By the use of a pulley (otherwise
known as a block and tackle), car Can you guess what the
mechanics lift 600 lb car engines mechanical advantage was of three
with one hand! Cranes that lift pulleys? Yup, three. The pulleys
steel girders and thousand pound tripled your strength. Who needs
air conditioning units are basically exercise when you have pulleys?
pulleys! (By the way, Archimedes
is credited for inventing the crane. So, you ready to do some weight
He actually used a crane as a lifting? The best way to learn about
weapon to defend Syracuse from this is to actually try it out. Let’s
Rome. When the Roman ships got
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