INTRODUCTION ABOUT MACHINES

As you look about you, you probably see half a
dozen machines that you don’t recognize as such.
Ordinarily you think of a machine as a complex
device-a gasoline engine or a typewriter. They are
machines; but so are a hammer, a screwdriver, a ship’s
wheel. A machine is any device that helps you to do
work. It may help by changing the amount of force or
the speed of action. A claw hammer, for example, is a
machine. You can use it to apply a large force for pulling
out a nail; a relatively small pull on the handle produces
a much greater force at the claws.
We use machines to transform energy. For example,
a generator transforms mechanical energy into electrical
energy. We use machines to transfer energy from one
place to another. For example, the connecting rods,
crankshaft, drive shaft, and rear axle of an automobile
transfer energy from the engine to the rear wheels.
Another use of machines is to multiply force. We
use a system of pulleys (a chain hoist, for example) to
lift a heavy load. The pulley system enables us to raise
the load by exerting a force that is smaller than the
weight of the load. We must exert this force over a
greater distance than the height through which the load
is raised; thus, the load will move slower than the chain
on which we pull. The machine enables us to gain force,
but only at the expense of speed.
Machines may also be used to multiply speed. The
best example of this is the bicycle, by which we gain
speed by exerting a greater force.
Machines are also used to change the direction of a
force. For example, the Signalman’s halyard enables
one end of the line to exert an upward force on a signal
flag while a downward force is exerted on the other end.
There are only six simple machines: the lever, the
block, the wheel and axle, the inclined plane, the screw,
and the gear. Physicists, however, recognize only two
basic principles in machines: those of the lever and the
inclined plane. The wheel and axle, block and tackle,
and gears may be considered levers. The wedge and the
screw use the principle of the inclined plane.
When you are familiar with the principles of these
simple machines, you can readily understand the operation of complex machines. Complex machines are merely combinations of two or more simple machines. Next post we will discuss about LEVERS,,,