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`pPrinciples of Physics

• Complete Problems 15-18

`gGeneral College Physics

• Complete Chapter 6 Problems  16, 18, 19, 22, 26, 30, 32, 33

• Read text Chapter 6, Sections 6 - 7

Introductory Problem Sets:

• Familiarize yourself with Introductory Problem Set 3, Problems 22-28, concerning kinetic and potential energy changes in a system.
• Familiarize yourself with Introductory Problem Set 5, the entire set.

Do and submit the second experiment on error analysis at http://www.vhcc.edu/dsmith/forms/Error_%20Analysis_II__Using_the_Data_Analysis_Program.htm (access at the Physics homepage > Assts, scroll to Assignment 7, click on link entitled 'Error Analysis Part II, Data Program' ).  This experiment requires data previously obtained with the TIMER program; alternatively new data may be easily and quickly acquired using this program.  The exercise introduces the Data Analysis Program (a link is provided within the form).

Forces exerted by Rubber Band Chains supporting identical weight, at different angles:

Data:

Use two chains, each of 8 rubber bands, but don’t use your calibrated chain.  Simply assume that the force vs. stretch characteristics of the chain you use are identical to those of your calibrated chain.

Measure the length of each chain when it suspends a bag holding 1 domino.

Suspend a bag holding 9 dominoes from both chains simultaneously, with both chains vertical.  Measure the common length of both chains.

Continue to suspend the 9 dominoes, but move the free ends of the chains until the two chains make an angle of 45 degrees with one another.  You can easily obtain a 45 degree angle by folding a sheet of paper.  Measure the length of each chain.

Repeat but with the chains at a 90 degree angle.

Analysis:

For each of the chain lengths you measured:

• Determine how much the chain has stretched from its 1-domino position.
• Determine how much force your calibrated chain would exert if it was stretched by the same amount from its 1-domino position.  The easiest way to do this is to have a good graph of force vs. length for your 1-domino chain.  (Another easy way is to have fit a linear function or, better, a third-degree polynomial to your force vs. length data and set up a spreadsheet using the coefficients of the linear function or polynomial to calculate the force for a given length, but you probably haven’t yet thought of doing that; this will be demonstrated in class).

Energy Released by Rubber bands vs. friction loss while sliding

Use the two chains to accelerate a block of 7 dominoes, as the chains ‘snap back’ from stretches of 5 cm, 10 cm, 15 cm and 20 cm past their 1-domino length.  See what maximum sliding distance you can achieve across a level, papered surface for each stretch.

Measure the length of each chain as it pulls the block of 7 dominoes across the papered surface, at a constant velocity.

Analysis:

Figure out how much energy should have been released during each ‘snap-back’, based on the force vs. length graph of your calibrated chain and on the 1-domino lengths of your actual chains.

Graph energy vs. maximum observed sliding distance.

For each chain length used to pull the dominoes across the surface at constant velocity, determine the force that would have been exerted by your calibrated chain if stretched by the same amount.  Average the two results to get a reasonable estimate of the force required to pull the block against frictional resistance across the papered surface.  Using this estimate, determine for each trial the work done against the frictional force by the sliding blocks.

Graph the work against the frictional force vs. the energy change of the rubber bands.