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course PHY 201
4/19 about 8:15 am
Experiment 7. Measuring MassesI have viewed and read through this lab.
Answer the following questions:
• Why is it essential that the balancing pans be placed at equal distances from the balancing point?
• How much would the result of weighing a 40 gram object be affected if one pan was positioned 29 cm from the balancing point, and the other 28 cm from this point?
• If when determining the mass of a small washer, the beam position could be brought to within .1 cm of its original position by a balancing mass of 1.21 grams, then what might be the mass of the washer?
• Why does the beam not balance at its equilibrium position when unequal masses are added at the two ends?
• Why does the beam not balance at its equilibrium position when equal masses are added at unequal distances from the balancing point?
The weight of the masses(because of the Torques about the fulcrum) will be different dependent upon how far the pans are from the fulcrum point.
The torques found from the F_g of 40 gram mass on both sides and moment arms would be 0.10967 N*m for 28 cm side and 0.11368 N*m for 29 cm side. The difference in these two is 0.00392 N*m. By dividing by g, we can obtain the units kg. This gives that that mass would vary by +/- 0.0004 kg, or +/- .4 g. On second thought, this would actually give units of kg*m or g*m. Would this distance of m in these units represent ‘dy? If so, this would possibly allow solving the next question.
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The .00392 N m difference in torques would be associated with a weight difference of about .00392 N m / .3 m = .01 N, corresonding to a mass difference of about .001 kg or 1 gram.
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I m not real sure how to figure out this third answer. I am sure that the result would be pretty close since it is within .1 cm though.
There is a greater force acting at the end with the greater mass, causing it to go down.
As shown in the answer to question 2, the moment arms are different, resulting in different torques, which allow the forces to rotate around the fulcrum.
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&#Good responses. See my notes and let me know if you have questions. &#