Efficiency

The efficiency of a trebuchet is a measure of how well the trebuchet performed compared to an ideal trebuchet. VirtualTrebuchet has two types of efficiency, Energy Efficiency, and Range Efficiency.

In the case of finding Energy Efficiency, an ideal trebuchet is one that converts all its potential energy before the launch onto kinetic energy and potential energy in the projectile at release. The expression for Energy Efficiency, ηenergy, is,

Since the ideal trebuchet gives all its energy to the projectile, the efficiency can be rewritten as,

A trebuchet with good Energy Efficiency does not necessarily shoot very far because the equation for Energy Efficiency ignores direction the projectile is launched. The projectile could be launched straight up so that it lands right back on the trebuchet, and the trebuchet may still have a good Energy Efficiency. This is why there is also Range Efficiency. For Range Efficiency, the ideal trebuchet is one that gives all its initial potential energy to the projectile, and launches it at 45° from horizontal. 45° is not usually the ideal release angle for a trebuchet, but that is because the projectile usually gains some extra velocity by staying in the sling longer. However, for a given launch velocity, 45° is the optimal angle to use to get the projectile to shoot the farthest possible. The ideal trebuchet ignores air resistance. The expression for Range Efficiency, ηrange, is,