course PHY 121
You're getting there. You had good answers to most of my questions. See my notes in response and see how this changes your tables, if it does.
Then send me your revision, with my original questions and my followup questions inserted along with your responses.
3 Rubber bands:
Pullback Prediction Slide Slide * rail N (0.294 N) F of Pullback (0.9 N per cm)
3 cm N/A 1.5 cm 0.444 cm * N 2.7 cm * N
4 cm 2 cm 2.5 cm 0.735 cm * N 3.6 cm *N
5 cm 3 cm 3.5 cm 1.029 cm * N 4.5 cm *N
6 cm 3 cm (1st prediction) 5.0 cm 1.470 cm * N 5.4 cm *N
7 cm 6 cm 6.0 cm 1.764 cm * N 6.3 cm *N
8 cm 7 cm 8.0 cm 2.352 cm * N 7.2 cm *N
9 cm 9 cm 10.0 cm 2.940 cm * N 8.1 cm *N
The force of the pullback would not be in N * cm. The tension in an individual rubber band is pullback in cm * 0.9 N / cm, which gives force in Newtons.
The way the tensions in the rubber bands combine and/or simply repeat themselves depends whether the rubber bands are in series or parallel.
See my notes below.
4 Rubber bands:
Pullback Prediction Slide Slide * rail N (0.294 N) F of Pullback (1.8 N per cm)
3 cm N/A 2.25 cm 0.662 cm * N 5.4 cm * N
4 cm 4 cm 4.25 cm 1.250 cm * N 7.2 cm * N
5 cm 6 cm 7.00 cm 2.058 cm * N 9.0 cm * N
6 cm 6 cm (1st prediction) 9.00 cm 2.646 cm * N 10.8 cm * N
I do not understand this experiment. I tried it up to this step:
For each pullback distance determine the force * distance total for the rubber band and for the rail as it slides across the floor.
• For each pullback distance you have the distance the rail slides. Multiply this distance, in cm, by the number of Newtons of force exerted by the rail as it slides across the floor.
• For each cm of pullback, determine the maximum and minimum forces exerted by the rubber band. Average these forces and multiply the average (in Newtons) by the 1 cm distance through which this approximate average force is applied.
I tried to calculate these steps (the last two columns in each table), but do not know if these are right and do not know where to go from here.
Questions you asked me to answer and resubmit:
Are these rubber bands in parallel or in series?
The first rubber bands are in series.
How much is each rubber band stretched if 3 rubber bands in series are stretched a total of 9 cm?
3 cm per rubber band.
How does the tension at the ends of a series of rubber bands compare to the tension in the middle?
I think it would be the same.
Right. Every rubber band would have the same tension, and the tension at the ends would therefore be the same as the tension in every rubber band.
The tension in every rubber band would the tension corresponding to a 3 cm stretch, not a 9 cm stretch.
This will reduce all your tensions in the first part be a factor of 3.
How are these rubber bands configured?
The second rubber bands are parallel.
I believe the configuration has two rubber bands in parallel, in series with 2 more rubber bands in parallel.
How would this change your results?
How long is each rubber band when the system is stretched 6 cm?
Each rubber band would be stretched 1.5 cm.
I modified my calculations in the table to correspond with my answers to these questions and my understanding now.
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