rubber band experiment 1 fall 05

Make a chain of 5 rubber bands, using paper clips as hooks between the bands and at the ends of the chain.  The rubber bands will be marked to number them 1 - 5.  DO NOT STRETCH THE RUBBER BANDS BEYOND 130% OF THEIR ORIGINAL LENGTH.  FOR EXAMPLE IF A RUBBER BAND IS 8 CM LONG IT SHOULD NOT BE STRETCHED TO MORE THAN 130% of 8 CM, OR 10.4 CM.  BE SURE NONE OF YOUR RUBBER BANDS IS EVERY STRETCHED TO MORE THAN 130% OF ITS MAXIMUM UNSTRETCHED LENGTH.

Lay down 3 sheets of 8.5 x 11 paper and tape them together to make a series of sheeds which is 8.5 x 33 inches.

Stretch out the rubber bands very slightly along the paper, so they just barely straighten out, and carfully and accurately mark the position of each end of each rubber band.  You will mark 10 positions.

Now repeat for 5 more trials, each time stretching the chain out a little more.  Increase the stretch in equal increments so that in the last stretch some of the rubber bands are stretched to nearly, but NOT OVER, their maximum safe length of 130% their maximum unstretched length.

Finally, using an accurate spring balance, make three stretches, one for a tension of 1 N, another for tension 2 N, and another for tension 3 N.

You will have marks for a total of 9 trials on an 8.5 x 33 inch series of papers. 

Measure as accurately as you can the position of each of the marks in each series.  The first mark will be taken to be at position 0, and should be at the end of your meter stick.  Without moving the meter stick measure the position of each mark.  You will get a series of 10 numbers, each indicating a position in cm.  For example your numbers might be

0, 9, 12, 20.2, 23.2, 31.7, 34.7, 43.1, 46.1, 54.9, 47.9.

From this series of numbers you will be able to determine the length of each rubber band (and also the length of each paper clip).

You will get 9 such series, with 10 numbers in each series.

This array of numbers will comprise your data for the experiment.

We will continue analysis in our next session.

For reference, you should also look at Mini Experiment 3, of which this is an adapted version.