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course Phy 241
October 7 around 10:40pm.
Questions about lab`qx001. Most of you found that the period of motion for the balance when the large paperclip was suspended in water was less than that for the straightened small paperclip. What were the two periods, and what was the ratio of the two?
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Period for small paperclip:
1st trial: 7
2nd trial: 7
Period for large paperclip:
1st trial: 2
2nd trial: 2
Ratio (large: small) 1: 3.5
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`qx002. Which system experiences the greater change in buoyant force when the clip goes a centimeter deeper.
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The system with the large paperclip because there is more of it down in the water.
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`qx003. Give your best explanation why you would expect the system with the large suspended paperclip to have the shorter period.
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Since the large paperclip has more weight, it takes longer for it to “make a period.”
the mass of the paperclip is very small compared to that of the entire system (actually we should talk about moment of inertia but we haven't deinfed that yet); so that difference shouldn't be a big deal
the buoyant force, however, differs very significantly; the system with the large clip experiences greater force trying to restore it to equilibrium
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`qx004. Speculate on whether the period of motion would remain constant through several cycles, if instead of a paperclip or wire the suspended object was a thin metal cone. What difference would it make if the cone was suspended from its apex as opposed to its base? What if instead of a cone the suspended object was a sphere? These are big open questions that can easily go beyond the scope of this course so don't spend an inordinate amount of time thinking about them, but do give the cone some thought. Hint: how would the buoyant force change with the depth to which the object is suspended in the water?
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I think the cone WOULDN’T remain constant because it’s kind of like jumping into a pool. If you jump off the diving board as straight as a pencil and point your toes downward, you’re obviously going to go down a lot faster than doing a belly buster. The way the cone is shaped has an effect on how it will come out of the water. The apex will go into the water a lot “smoother” than the base. My guess would be that a sphere WOULD have somewhat of a constant period of motion.
The buoyant force would change, with the depth to which the object is suspended in water, by however much the object’s mass is and therefore relating to the “Law of Archimedes,” the buoyant force is equal to the displacement of the water.
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Very good. See my notes.
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