1. The problem statement, all variables and given/known data How would you find the energy efficiency of a torsion catapult ? (one i built for project) I have the Force at which im pulling the arm. F = 20N also the angle from origin to the point of release ( or when the ball leaves the arm) Theta = 50 degrees 2. Relevant equations Energy Efficiency = Energy Output/ Energy Input E input = 3. The attempt at a solution i have filmed the trajectory of my catapult using Video camera and logger pro software. i do have velocity and acceleration in both x and y directions. But how do i exactly find the Input energy of this particular system?