# Inertia of Weight

Inertia of Weight is the moment of inertia of the counterweight around its center of gravity.

The moment of inertia can be found by breaking the weight up into simple shapes, finding the moment of inertia for each one, and then combining them together using the parallel axis theorem. A list of formulas for the moment of inertia of different shapes can be found here. The Arm Example Calculations show how to do this for the arm. A similar procedure can be used for the weight.

Alternatly, using a 3D CAD software package is probably the easiest way to find the inertia of the weight.

In general, it is better to have a weight with a small inertia. However a larger inertia comes with a heavier weight. The easiest way to get around this is by having a weight that is able to pivot. If you do this you can set the inertia of the weight to a small number.

# Mass of Weight

Mass of Weight is the mass of the counterweight.

In general, the projectile will go farther with a heavier counterweight.

 Units English (feet)English (inches)Metric Length of Short Arm ft Length of Long Arm ft Length of Sling ft Length of Weight ft Height of Pivot ft Uniform arm Mass of Arm lb Inertia of Arm lb·ft² Pivot to Arm CG ft Mass of Weight lb Inertia of Weight lb·ft² Projectile BaseballGolf BallPumpkinCowCustom Mass of Projectile lb Projectile Diameter ft Wind Speed ft/s Release Angle ° Play speed: 1x Link to save this trebuchet

## VirtualTrebuchet 2.0

VirtualTrebuchet is a web based trebuchet simulator that will allow you to quickly evaluate different trebuchet configurations.

1. To begin, enter the parameters of your trebuchet in the input boxes.
2. Next, press the "Simulate" button located under the inputs.
3. Finally, watch your trebuchet go.