# Dynamics Final

1. Apr 27, 2009

### BuickBoy

This is a catapult design project.

1. The problem statement, all variables and given/known data
The counterweight is 400lb, the boulder (projectile) is 50lb and the throwing arm is 100lb. The throwing arm is assumed to be rigid, uniform in density, and weight. The throwing arm is also 17ft in total length. The throwing arm starts at forty degrees and rotates about a pivot point counterclockwise, which launches the boulder from a chosen (optimal) angle. The pivot point is 12ft above the ground.

Determine the center mass of the launch subsystem, mass moment of inertia of the launch subsystem about its center of mass (assuming the throwing arm is a long slender rod and the counterweight and boulder are not point loads), mass moment of inertia of the launch subsystem about the pivot point, comparing results of the mass moments of inertia and comment on the results relative to the efficiency of a catapult system, usisng the concepts of work and energy , determine the boulders release speed, and calculate the maximum launching distance of your optimized catapult design.

The final steps include assuming W (omega) of the sling is equal to 1.5 x W(omega)of the launch arm. (This part I dont really need help with

2. Relevant equations

Work and Energy Equations

3. The attempt at a solution

Without having to type out my current work, I'm just trying to get started. The class is very vague. I started trying to calculate the velocity of the arm as it would rotate to the bottom of the support using the same concepts of a pendulum, I figured if I could assume each side of the pinned throwing arm was half of a pendulum the difference in the velocities would be accurate. I was told I'm wrong. Back to square 1.