### Hooke's Law

Laboratory 52 investigated Hooke's Law using readily available local materials, styrofoam cups, marbles, and elastic bands.

Norma adds marbles to the cup while Leilani steadies the cup using two meter sticks. Building off of the procedure developed summer 2010, teams of three worked together. Leilani keeps the cup steady and reads off the displacement, Norma adds marbles. A third member, not pictures, records the displacement.

The new twist this fall was that after seeing data for this lab over the past three terms I had come to realize that small differences in marble mass were not significantly affecting the the data.

This fall the students first massed an empty cup, then massed all thirty marbles at one time. After subtracting the cup mass, the mass of the thirty marbles was divided by thirty to obtain the average mass per marble. This was rounded to 0.1 grams and the value obtained was used as the mass for every marble.

The average mass of the duck marbles varied more than I might have expected, ranging from 5.0 grams to 5.4 grams.

This removed the need to mass each marble individually, which was time consuming and interrupted the process of observing the elastic stretch. The elastic behaves non-linearly at times, and this can be better seen in the faster, more efficient process developed this fall.
At the top of the board can be seen remnants of the new procedure.

Most schools here lack triple beam mass balances. Yet this experiment can be done without a beam balance by simply assigning a mass to the marbles. For all intents and purposes a mass of five grams per duck marble can be assumed when no mass information is known.
Adam adds marbles, Yvonne steadies the meter stick and cup, Tellez enters the data. This is the set-up that appears to work best for gathering data.
Lupe steadies the cup to read the total drop, Monalisa waits to add another marble. Steadying the cup without supporting the cup is the challenge.