Simple Machines
Work and Machines
-Simple machine: machine that does work with only one movement of the machine.
There are six types of simple machines: lever, pulley, wheel and axle,inclined plane, screw, and
wedge. The pulley and the wheel and axle are modified levers, and the screw and the wedge
are modified inclined planes.
-Lever: simple machine consisting of a bar free to pivot around a fixed point called the fulcrum.
There are three classes of levers and the differences among the three classes of levers depend
on the location of the fulcrum, the input force and the output force.
A. First-class lever: lever with the fulcrum located between between the input and output
forces. The output force is always in the opposite direction to the input force in a first-class
lever.
B. Second-class lever:
lever where the output
f o r c e e x e r t e d i s
between the input
force and fulcrum. For
a second-class lever,
the output force is
always greater than
the input force.
C. Third-class lever:
lever where the input
f or ce i s a pp l i e d
between the output
force and the fulcrum.
The output force is
always less than the
input force in a third-
class lever, but the
distance over which
the output force is
applied is increased.
IMA of lever = length of input arm / length of output arm
Mr. Saoulis
