Catapult:
Any machine that hurls a projectile.
• “Kata” means downward.
• “Peltos” refers to a small circular shield carried in battle.
• “Katapultos” was taken to mean “shield striker.”
A catapult is a machine
that fires objects known
as projectiles by first
storing potential energy.
When activated, the
potential energy is
quickly converted to
kinetic energy. The
kinetic energy creates
an unbalanced force
that can be used
to accelerate
the projectile.
We typically think of a
catapult as something that
was used in the Middle
Ages to destroy the walls of
a castle.
But Catapults have a very long history, dating long before the time of
castles. The first catapults most likely originated independently in
Greece and China around the 4th Century BC. However, unique
catapult designs were developed and used by many different cultures
over the centuries.
The Trebuchet is probably the oldest type of catapult. It was invented either by
the Chinese or by a culture located in the Middle East. Trebuchets were used
mainly as lobbing machines to spread fire and diseased corpses, as well as a
lot of solid missiles, over the walls of castles to rain down on the inhabitants.
They were very effective!
The next oldest type of catapult is the
Ballista. The earliest form of the
ballista is thought to have been
developed for Dionysius of Syracuse,
circa 400 BCE. Ballistae typically were
used for lighter but more accurate
projectiles, and could be easily
modified to shoot either spherical or
shaft projectiles, allowing their crews
to adapt easily to prevailing battlefield
situations in real time. Ballistae were
even mounted on warships and used
to hurl fire onto other ships.
The Romans took the ballista, used it, and then
improved in in the Roman way to create the
Onager. Not much is known about how these
machines really looked, but our best guess is
something like this one. Onagers were used
right up to the middle ages alongside the
Trebuchet, when gunpowder and the cannon
were invented and eventually replaced the
catapults.
Another example of a ballista.
Modern aircraft
carriers use
catapults to launch
aircraft on short
runways.
Catapult Challenge:
Design and build your own marshmallow catapult! You may only
use the following supplies in this challenge:
•1 plastic spoon.
•No more than 6 popsicle sticks (either size).
•No more than 3 wooden dowels.
•No more than 12 rubber bands.
•Masking tape.
•You must use a block or brick as a base.
•Your catapult must be placed on the ground or on a table when launching.
•2 Marshmallows.
Objective: We will be testing accuracy, precision, and distance.
Get started with a sketch right now!
Accuracy refers to how close a measurement
(observation) is to the expected or desired target value.
The farther a measurement is from its expected value,
the less accurate it is. All of the observations above hit
the target, so they are all somewhat accurate. The ones
near the bulls-eye are more accurate than the others,
because they are close to the desired target.
Precision refers to closeness of a set of repeated
measurements (observations). The observations on the
target above are closely clustered together; these
observations are considered to have high degree of
precision. However, since they are not in the bulls-eye,
they are not very accurate!
The observations on the target above are
both precise (closely grouped) and accurate
(close to the desired target).