Lab 20

Lab 20 / Experiment 8: Conservation of Angular Momentum

November 21 2016

Goal:

We are testing our understanding of the conservation of angular momentum.  To address this goal, we will launch a ball at a device that simulates an inelastic collision; this device is mounted on a rotating disk that we can measure the angular velocity of. We will compare our predicted outcome to our experimental outcome.

Procedure and Analysis:

The device used to launch  our ball is a angled track which will accelerate the ball in a predictable way to a velocity we can calculate. The ball then exits the track and collides with the disk-mounted device. The ball sticks to the device and transfers its energy into our disk-system. This type of collision is one we are very familiar with, and we will use our concepts of conservation of angular momentum to assess the final angular velocity.

Our apparatus for today's experiment.

First we must find how fast the ball leaves it's launch track.

We must then assess the angular momentum of our system. Since angular momentum is conserved, this gives us a clear method to find our angular velocity after the ball has stuck to the disk-system.

This is our experimental angular velocity. The class shared the experimental data, so most of the hard work was done by Professor Wolfe. Thanks Professor.

trial 1

w predicted: 2.434 rad/s

w actual:      2.259 rad/s

trial 2

w predicted: 1.436 rad/s

w actual:      1.353 rad/s

Conclusions:

Our experimental(actual) omegas closely match our predicted omega values.  Hurray! This confirms that our knowledge of conservation of angular momentum is sufficient for modeling this experiment. Although our predicted numbers have some small error, we cannot overlook how close we have come to accurately assessing physical scenarios. Possible sources of error include assumptions of the system being perfect inelastic, and errors in measuring placement of the ball which affects our disk-system inertia analysis.