for use with materialworlds Siege engine simulation
© materialworlds.com 2001
1. In action simulation
a) Describe and explain the forces between the bricks in the wall before it is hit by the ball.
b) How does the siege engine move after throwing the ball? Why?
c) When the ball hits the wall, what forces are they both subjected to and what are their effects?
d) Copy the energy graph, adding labeled vertical lines to indicate significant events.
Describe and explain the energy changes that occur.
2. Close up simulation
Pause and rewind the simulation.
a) Describe the forces acting initially around different points of the siege engine.
b) How do these forces change as the siege engine throws the ball?
(in particular - how does the siege engine interact with the ground?)
c) What happens if you select both siege engine and ball and lift them off the ground before launching the ball?
As the ball is launched, the kinetic energy of the whole system (ball and siege engine) steadily increases and its potential energy decreases.
d) What type of potential energy is decreasing?
Although kinetic energy is increasing, it's not increasing as fast as potential energy is decreasing (i.e. the total energy of the system is decreasing).
e) What would this lead you to say about the siege engine?
Just after the ball is released, the kinetic energy of the system falls suddenly.
f) What exactly has lost kinetic energy and why? Does it matter?
g) After you've lost sight of the ball, how does the energy graph tell you about its motion?
3. Experiment simulation
When you first run this simulation the siege engine fires without a projectile loaded.
a) What happens? Why?
Now try launching different sizes and forms of projectile:
Pause
Rewind
Load catapult (drag a projectile into position - then click elsewhere on the page so it doesn't stay selected)
Play All the projectiles are of the same density - so you can assume the larger ones have a greater mass.
b) How does the mass of the projectile affect its and the siege engine's behaviour?
c) What difference (if any) does the alternative form of projectile (double-ball) make?
4. Links
Follow the links on the information side panel to find out about historical examples of siege engines.
a) How do the methods of propulsion (and the behaviour) of real siege engines compare with this simulation?
Are there any interesting similarities or differences?
b) Which real siege engine has a method of releasing the projectile similar to that acheived by the double-ball projectile in this simulation?