BALLISTABy Blade Maczuga

Ballista mechanics

The Ballista was created by the Greeks using their new innovation called the Torsion spring.

A Torsion spring is when a spun rope or string has a force to unwind back to it’s original position, just think of how a wound rubber band spins when you release it

Ballista mechanics (cont.)

A Ballista uses two of these Torsion springs

They are connected to flexible throwing arms and can be pulled down to twist the Torsion springs

Ballista mechanics (cont.)

How the Ballista works with these Torsion springs (which are both spun in completely opposite directions) is that when you pull back on the main rope which in turn twist the two hardy throwing arms that are connected to the Torsion springs which winds them up further creating a great force if released.

This device was used to fire bolts of different kinds and rocks (before being used for mostly bolts)

Ballista in regard to Physics

The main aspects in a Ballista that involve Physics have to do with Force (torsion springs) and Projectile motion (the bolt/ammo)

Torsion springs can be applied to Hooke’s law by that a force is required to keep the torsion springs spun to maintain the force that is trying to bring the Torsion springs to unwind.

Ballista force

A Ballista can come in many sizes all of which can change the force applied to the bolt greatly.

The size of the bolt can also change the impact it has on targets some bolts were up to 10 pounds and caused great damage during sieges.

Projectile Motion

A Ballista when firing will have a great force applied to the bolt when the rope attached to the throwing arms.

This great force will be applied to the bolt and it will be sent a great distance depending on the size of the Ballista and it’s components.

The Projectile will fly high in the sky with the force from the torsion springs, gravity, and wind resistance.

Projectile Motion (cont.)

The distance the bolt travels will be great as it was used a great siege weapon in Medieval times.

Insight into the Ballista

Before I did this project I didn’t really know that much about the Ballista, I thought it worked kind of like a crossbow, but it used greater Greek technology such as Torsion springs to create a great force

I think this was a great siege weapon in the past and has a very interesting history that goes along with it from Greek to being revamped by the Romans

Bibliography

http://medievallifestyle.com/siege-engines/ballista.html

http://www.mlahanas.de/Greeks/war/CatapultTypes.htm

http://www.howtobuildcatapults.com/roman_ballista_plans.html

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