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course PHY 241
01/13/20128:47 pm
Coefficient of Restitution (University Physics only)
You observed drop heights and bounce heights for a number of different spherical objects.
Insert a copy of your data here, along with any previously submitted work you wish to include:
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Drop Distance Item Bounce Distance
20 cm small marble 15cm, 14cm, 15 cm
40 cm small marble 28 cm, 29 cm, 24 cm
20 cm green bb 19.5 cm, 19 cm, 19.5 cm
20 cm large marble 9cm, 10cm, 10cm, 10cm
40 cm large marble 21cm, 23cm
60 cm large marble 30cm, 29cm, 30cm
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Each object was dropped from three different heights. Did each different object appear to bounce back to the same proportion of its original height, independent of drop height, or does there appear to be some systematic change in this result with drop height? Would you expect the answer to differ for different objects?
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There is a change. It would appear that heavier objects bounce back at a decreased percentage of height compared to lighter objects
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To determine the coefficient of restitution for a given object from a given height, which would be more appropriate under the actual circumstances of your experiment?
• use the average of the five observed bounce heights
• use the average of the three greatest observed bounce heights
• use the maximum of the observed bounce heights
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use the average
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Choosing one of three alternatives does not constitute an answer.
An answer needs to include the reasoning that led to it, and should weight the merits of all three choices.
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For a given object, of the three percents (bounce height as percent of drop height) obtained for the three different drop heights, which would give you the best indication of the coefficient of restitution and why?
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the middle one generally
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Again you need to provide reasoning and consider all alternatives.
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What happened to the coefficient of restitution as you went from a small marble to a larger marble? If there was a trend, would you expect it to continue as marble size continues to increase? What else would you expect to happen if you continued to increase marble size?
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The coefficient decreased, meaning the object lost more of its energy. And yes, I would expect that if we increased the size of our objects even further, we would receive results of an increased trend.
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The coefficient of restitution of an object is defined to be the ratio of the normal speed of the object before collision with a rigid elastic body to its normal speed after collision, with speeds measured relative to the rigid object. (‘Normal’ refers to the component of the speed in the direction perpendicular to the plane of contact of the two objects; for a sphere dropped onto a level floor the normal direction is vertical).
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According to your observations, what was the coefficient of restitution of each object?
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Don’t have the speed of objects
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This can be determined from drop height and bounce height, assuming the acceleration to be close to the acceleration of gravity.
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What factors might result in inaccuracies in your results?
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We eyeballed most of the measurements, meaning there was a greater chance of inaccuracy in data gathering.
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Data look good, but you don't include much detail in your reasoning.
&#Please see my notes and, unless my notes indicate that revision is optional, submit a copy of this document with revisions and/or questions, and mark your insertions with &&&& (please mark each insertion at the beginning and at the end).
Be sure to include the entire document, including my notes.
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