# Simple Machines for Kids: Science and Engineering for Children – FreeSchool

You’re watching FreeSchool! Hi everyone! Today we’re going to talk about
simple machines. A simple machine is a device that makes work
easier by magnifying or changing the direction of a force. That means that simple machines
allow someone to do the same work with less effort! Simple machines have been known since
prehistoric times and were used to help build the amazing structures left behind by ancient
cultures. The Greek philosopher Archimedes identified
three simple machines more than 2,000 years ago: the lever, the pulley, and the screw.
He discovered that a lever would create a mechanical advantage, which means that using
a lever would allow a person to move something that would normally be too heavy for them
to shift. Archimedes said that with a long enough lever and a place to rest it, a person
could move the world. Over the next few centuries more simple machines
were recognized but it was less than 450 years ago that the last of the simple machines,
the inclined plane, was identified. There are six types of simple machines: the
Lever, the Wheel and Axle, the Pulley, the Inclined plane, the Wedge, and the Screw.
Pulleys and Wheel and Axles are both a type of Lever. Wedges and Screws are both types
of Inclined Planes. Each type of Simple Machine has a specific purpose and way they help do
work. When speaking of simple machines, ‘work’ means
using energy to move an object across a distance. The further you have to move the object, the
more energy it takes to move it. Let’s see how each type of simple machine helps do work. A LEVER is a tool like a bar or rod that sits
and turns on a fixed support called a fulcrum. When you use a lever, you apply a small force
over a long distance, and the lever converts it to a larger force over a shorter distance.
Some examples of levers are seesaws, crowbars, and tweezers. A Wheel and Axle is easy to recognize. It
consists of a wheel with a rod in the middle. You probably already know that it’s easier
to move something heavy if you can put it in something with wheels, but you might not
know why. For one thing, using wheels reduces the friction – or resistance between surfaces
– between the load and the ground. Secondly, much like the lever, a smaller force applied
to the rim of the wheel is converted to a larger force traveling a smaller distance
at the axle. Wheel and axles are used for machines such as cars, bicycles, and scooters,
but they are also used in other ways, like doorknobs and pencil sharpeners. A Pulley is a machine that uses a wheel with
a rope wrapped around it. The wheel often has a groove in it, which the rope fits into.
One end of the rope goes around the load, and the other end is where you apply the force.
Pulleys can be used to move loads or change the direction of the force you are using,
and help make work easier by allowing you to spread a weaker force out along a longer
path to accomplish a job. By linking multiple pulleys together, you can do the same job
with even less force, because you are applying the force along a much longer distance. Pulleys
may be used to raise and lower flags, blinds, or sails, and are used to help raise and lower
elevators. An Inclined Plane is a flat surface with one
end higher than the other. Inclined planes allow loads to slide up to a higher level
instead of being lifted, which allows the work to be accomplished with a smaller force
spread over a longer distance. You may recognize an inclined plane as the simple machine used
in ramps and slides. A Wedge is simply two inclined planes placed
back to back. It is used to push two objects apart. A smaller force applied to the back
of the wedge is converted to a greater force in a small area at the tip of the wedge. Examples
of wedges are axes, knives, and chisels. A Screw is basically an inclined plane wrapped
around a pole. Screws can be used to hold things together or to lift things. Just like
the inclined plane, the longer the path the force takes, the less force is required to
do the work. Screws with more threads take less force to do a job since the force has
to travel a longer distance. Examples of screws are screws, nuts, bolts, jar lids, and lightbulbs. These six simple machines can be combined
to form compound or complex machines, and are considered by some to be the foundation
of all machinery. For example, a wheelbarrow is made of levers combined with a wheel and
axle. A pair of scissors is another complex machine: the two blades are wedges, but they
are connected by a lever that allows them to come together and cut. We use simple machines to help us do work
every day. Every time you open a door or a bottle, cut up your food, or even just climb
stairs, you are using simple machines. Take a look and see if you can identify the simple
machines around you and figure out how they make it easier to do work.