Definition
2: The mechanical
advantage (MA) is
the factor by which a machine multiplies the force put into it.
Definition
3: The effort arm represents where force is input. The effort arm is always larger
than the resistance arm.
How
do we Calculate Mechanical Advantage of a Lever-
For
the Lever:
MA = length of effort arm ÷ length of resistance arm.
About
the Lever
Early
studies
The earliest
remaining writings regarding levers date from the 3rd century BC and were provided
by Archimedes. Give me the place to stand, and I shall move the earth is
a remark of Archimedes who formally stated the correct mathematical principle
of levers (quoted by Pappus of Alexandria).
In
ancient Egypt, constructors used the lever to move and uplift obelisks weighting
more than 100 tons.
Force
and levers
The
force applied (at end points of the lever) is proportional to the ratio of the
length of the lever arm measured between the fulcrum and application point of
the force applied at each end of the lever. Mathematically, this is expressed
by M = Fd.
What
are the three classes of levers
There
are three classes of levers representing variations in the location of the fulcrum
and the input and output forces.
First-class
levers
Examples:
- Seesaw (also known as a
teeter-totter)
- Crowbar
- Pliers (double lever)
- Scissors (double
lever)
Second-class
levers
Examples:
- Wheelbarrow
- Nutcracker
(double lever)
- The
handle of a pair of nail clippers
- An
oar
Third-class
levers
Examples:
- Human arm
- Tongs
(double lever) (where hinged at one end, the style with a central pivot is first-class)
- Catapult
- Any
number of tools, such as a hoe or scythe
- The
main body of a pair of nail clippers, in which the handle exerts the incoming
force
