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course PHY241
do not understand the last experiment
Atwood System:The Atwood system consists of the paperclips suspended over the pulley. A total of six large clips connected by a thread were suspended,
three from each side of the pulley. The system was released and, one side being slightly more massive than the other due to inconsistencies in the
masses of the clips, accelerated from rest, with one side descending and the other ascending. The system accelerated through 50 cm in a time interval
between 4 and 6 seconds; everyone used their 8-count to more accurately estimate the interval. Then a small clip was attached to the side that had
previously ascended. This side now descended and the system was observed to now descend is an interval that probably lasted between 1 and 2 seconds.
If you weren't in class you can assume time intervals of 5 seconds and 1.5 seconds. Alternatively you can wait until tomorrow and observe the system
yourself; the initial observation requires only a couple of minutes.
`qx001. What were your counts for the 50 cm descent of the Atwood system?
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4.2s for 3 lg paperclips
1.8s for the extra small clip
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`qx002. What were the two accelerations?
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5.67cm/s^2
30.86cm/s^2
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`qx003. Why did the systems accelerate?
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Because of gravity and uneven weights
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`qx004. Suppose the large paperclips all had mass 10 grams, the small clip a mass of 1 gram. What then was the net force accelerating the system on
the first trial, and what was the net force on the second?
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340.2g*cm/s^2,6total lg paperclips
1882.47g*cm/S^2,6lg +1sm
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.. if uncertainty +-1%
`qx005. Given the masses assumed in the preceding, what is the force acting on each side of the system? What therefore is the net force on the
system?
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170.1g*cm/S^2,0. half of the previous on each side. But accelerating in opposite directions so 0 for system?
system direction would be clockwise or counterclockwise; in either of these directions one clipe would be going up and the other down, so up and down don't describe the direction of motion or acceleration.
925.8g*cm/s^2 for the 3lrg clips,956.66 for 3lrg+1sm.30.86g*cm/s^2 for system.3lg clips going up (- direction)
??????????????
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`qx006. Based on your counts and the resulting accelerations, do you think the ratio of the masses of the large to small paperclips is greater than,
or less than, the 10-to-1 ratio assumed in the preceding two questions?
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less than a 10:1 ratio
you should give your reasoning
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`qx007. If the mass of each larger clip is M and the mass of a smaller clip is m, what would be the expressions for the net force accelerating the
system? What would be the expression for the acceleration of the system?
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Fnet=(6M)a,Fnet=(6M+m)a
a=(Fnet)/6M,a=Fnet/(6M+m)
Fnet would just be m a. The 3 M on each side will be in balance and will make zero contribution to net force.
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`qx008. If the mass of the each of the larger clips is considered accurate to within +-1%:, would this be sufficient to explain the acceleration
observed when 3 large clips were hung from each side?
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yes
you need to explain your thinking
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... sample the accelerations for random divisions of the six large clips ... predict what the distribution of masses would look like ...
Magnet and Balance
Everyone was given a small magnet and asked to achieve a state where the balance was in an equilibrium position significantly different from that
observed without the magnet. It was suggested that the length of the suspended clip beneath the surface of the water should differ by at least a
centimeter.
... assuming 1 mm diam ...
`qx009. Describe in a few lines your efforts to achieve the desired result. What worked, what didn't, what difficulties presented themselves, etc.?
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Put a meter stick behind the balance and slowly lowered the magnet closer to the balance until it moved. Initially it just completely grabbed the
balance, but after looking closer it barely moved the balance and stayed before it got close enough to grab it
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`qx010. How much difference was there in the length of clip suspended in the water? If you didn't actually measure this, give a reasonable estimate.
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when the magnet moved the system, the amount of clip hanging in the water changed
the question is by how much it changed
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`qx011. How did you adjust the magnet? If you wanted to quickly increase or decrease the length of the suspended paper clip beneath the surface by 1
millimeter, using only what you had in front of you during the experiment, how would you go about it?
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`qx012. Assuming the diameter of the suspended clip to be 1 millimeter, by how much did the buoyant force on the suspended clip change? How much
force do you therefore infer the magnet exerted? If you have accurate measurements, then use them. Otherwise use estimates of the positions of
various components as a basis for your responses.
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&#Good responses. Let me know if you have questions. &#
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