Catapult
History
Concept
LEVERS
Science (ACSSU117)
Maths (ACMNA240)
GRAVITY
Science (ACSSU118)
The catapult has many forms but the classic sprung arm style is
otherwise known as the mangonel and appeared as a siege engine in
the first few centuries AD. They had an effective range of up to
approximately 450m which was extended with clever extensions of
the throwing arm with an extended sling. This was known as a
trebuchet and was responsible for leveling many medieval castles.
Additional Reading: http://www.stormthecastle.com/catapult
/the-history-of-the-catapult.htm
Scientific Principles Involved
ENERGY IN ELASTIC
BAND
Science (ACSSU115,
ACSSU190)
The basic principle behind the classic catapult involves and
understanding of:
Levers.
The throwing arm is a simple lever and an understanding of levers
enabled the variation to be developed that became known as the
trebuchet.
PARABOLIC MOTION
Science (ACSSU229)
Maths (ACMMG223,
ACMNA239)
Conservation of energy.
The transfer of energy from either a counter weight or springs (often
made of twisted rope) to kinetic energy to throw the projectile
through the air.
Gravity and parabolic motion.
To understand how to clear a wall (often with burning pitch or
disease infested dead bodies) or impact on the wall with heavy
stone to break it down an understanding of trajectory and launch
angle was required. This experience could be drawn from a
thousand years of warfare with slings, javelins and arrows.
Resources
Moments
A short sequence of slides showing the concept of moments
around a fulcrum, explaining the relationship between the
force and distance from the fulcrum.
http://lrrpublic.cli.det.nsw.edu.au/lrrSecure/Sites/Web/skoool
/phys/step/calc_moments/index.html
Elastic Energy
A short sequence of slides showing the concept of energy
being stored in a spring and the relationship between the
stretched spring and energy stored.
http://lrrpublic.cli.det.nsw.edu.au/lrrSecure/Sites/Web/skoool
/phys/step/stretching_mat/index.html
Levers
A practical experiment to investigate how levers can be used to lift
weights and the effect of changing arm lengths in the ability to lift
different weights with different force.
http://www.sciencebuddies.org/science-fair-projects/project_ideas
/Phys_p065.shtml
Levers and Load
A practical experiment to investigate how levers can be used to lift
weights and the effect of moving the fulcrum in the ability to lift
different weights with different force.
http://www.sciencebuddies.org/science-fair-projects/project_ideas
/Phys_p014.shtml
Simple Catapult
A short practical experiment where you build a small catapult with
paddle pop sticks to throw a ping pong ball.
http://www.superchargedscience.com/science-catapults.htm
Extension Learning
Discussions of the best arrangement of a lever arm for a
catapult can include moments which are really just a simple
linear equation which year 9 and 10 students should be familiar
with: moment = force x radius