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Catapult Physics and simple machines

Make physics fun by exploring motion through the art of warfare. Look at the history of catapults, try an interactive of projectile motion and build your own catapult or trebuchet.
by

Jodi Gulley

on 29 November 2012

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Transcript of Catapult Physics and simple machines

Catapult Physics and Simple Machines Warwick Castle (UK) re-enactment Catapults and Trebuchets at war Medieval Weapons Project: Make your own catapult Physics of Weapons Catapult physics is the use of stored energy to hurl a projectile (the payload), before the use of explosives was invented.

Catapults use tension or torsion in the form of elastic, twisted rope or some other form of flexible material.

Trebuchets use a counterweight as a source of gravitational potential energy.

The three primary energy storage mechanisms for catapults are tension and torsion, and for trebuchets -gravity. http://www.youtube.com/watch?v=9faom6z5dZ0 Projectile Motion In physics, the ballistic trajectory of a projectile is the path that a thrown or launched projectile will take under the action of gravity, neglecting all other forces, such as friction from air resistance, without propulsion. http://phet.colorado.edu/en/simulation/projectile-motion History of Catapults Catapults may have originated in China between 400-300BC. Through the ages catapults were mainly used as weapons to throw missiles( rocks, carcasses, flaming objects) Early catapults were much like the crossbows and stood nearly 3 metres tall. They appear to have been used in Greece around this time also. By the 14th Century catapults had been replaced by cannons. We mostly think of catapults from the middleages 12th Century England. Battering rams, Ballistas and Trebuchets The Battering Ram and the Bore were used to literally 'batter' down, pound, punch and shake and drill into castle gates, doors and walls. Lord of the Rings. The ballista is similar in principle to a crossbow, but much larger.
Like the torsion powered mangonel, it used twisted rope as the energy source. The picture shows the torsion mechanism consisting of twisted rope, located at the pivot location of the two side arms. The massive Trebuchet consisted of a lever and a sling and was capable of hurling stones weighing 100 kg with a range of up to about 300 metres. Trebuchet The trebuchet was often preferred over a catapult due to its greater range capability and greater accuracy due to using the counter weight. A trebuchet works by using the energy of a falling (and hinged) counterweight to launch a projectile (the payload), using mechanical advantage to achieve a high launch speed. For maximum launch speed the counterweight must be much heavier than the payload, since this means that it will "fall" quickly. The Onager is a type of catapult that uses torsional pressure, generally from twisted rope, to store energy for the shot. CATAPULTS The Leonardo da Vinci Catapult (1500s) Bibliography www.real-world-physics-problems.com
http://www.catapults.info/
http://tuhsphysics.ttsd.k12.or.us/Research/IB04/JonePeytShri/index.htm
http://www.dynamicscience.com.au/tester/solutions/hydraulicus/simplemachineslevers4.htm
www.edheads.org/activities/simple-machines
http://phet.colorado.edu/en/simulation/projectile-motion
You tubes: Rich english guy and his trebuchet
Floating arm trebuchet, the most effective catapult
Catapult sect 11
The legendary shots: catapult shot
LOTR gothmog versus large projectiles MODELS Design Brief Engineering Challenge Catapult Challenge: With less than $100 budget, construct a catapult that can be moved by simple machines through the gates (square 30cm x 30 cm) and up a ramp (10 degree inclined plane and 20cm long) to a platform. The aim is to then fire a package (projectile) from the catapult as far and accurate as possible.

Use your knowledge of simple machines (inclined planes, pulleys, levers, wheels, axles). Measures include: distance the projectile travels and accuracy to complete the operation.

Constraints for your design include:
1. Size of the catapult
2. Using only the materials outlined
3. Spending less than $100 for the materials
4. All catapults have a projectile of the same mass (one lolly)
5. Only simple machines may move the catapult
6. You can test three times and record your results in the Testing Results Table.
7. There must be at least three objective judges for the operation (Judge 1 assesses the accuracy and distance of the throw; Judge 2 ensures the rules are followed; Judge 3 calculates the overall score; Judge 4 ensures fairness of judging).
Judges must sign the Best Results Table for your results to count.

Prices Materials Prices Materials
$2 Paddle Pop $2 Cotton reel
$3 Piece of string per 30cm $1 Skewer
$3 Rubber Band $0.50 Straw
$3 Dowel $2 Plastic spoon
$0.50 Plastic-headed thumb tacks $1 Sticky tape (10cm) LOTR Gothmog versus projectiles
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