OpenQuery1

course PHY 121

7/19

ph1 query 1*********************************************

Question: Explain in your own words how the standard deviation of a set of numbers is calculated.

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Your solution: To calculate the standard deviation of a set of numbers, you first find the mean of the set. Then, you find the deviation of each trial from the mean. Square the deviations, then average them. If there are less than 30 squared deviations to average, subtract 1 from the total number of terms and divide by that. If there are more than 30, just use the actual number of terms. Take the square root of the average deviation; this is your standard deviation.

Confidence rating: 2/3

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Question: Explain in your own words the process of fitting a straight line to a graph of y vs. x data, and briefly discuss the nature of the uncertainties encountered in the process. For example, you might address the question of how two different people, given the same graph, might obtain different results for the slope and the vertical intercept.

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Your solution: To fit a straight line to a graph of data, you need to take into account all of the points and develop some kind of estimate as to what line would pass through all of the points as evenly as possible. There is uncertainty in doing this by hand because one person might see the points as best fitted one way, while someone else may see them at a higher angle or position on the graph. It’s hard to take into account all of the different points, especially when they are really scattered.

Confidence rating: 3

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Question: Briefly state what you think velocity is and how you think it is an example of a rate.

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Your solution: Velocity is a measure of how fast something is moving over a certain period of time. It is an example of a rate because it measures one condition in reference to another.

Confidence rating: 2/3

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Given Solution: A rate is a change in something divided by a change in something else.

This question concerns velocity, which is the rate of change of position: change in position divided by change in clock time. **

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Self-critique (if necessary): I got the “rate” part but didn’t use the correct terminology when describing velocity. I understand that it is “change in position” and not “how fast”.

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Question: Given average speed and time interval how do you find distance moved?

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Your solution: To find the distance travelled, you would multiply the average speed times the time interval.

Confidence rating: 3

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Given Solution: ** You multiply average speed * time interval to find distance moved.

For example, 50 miles / hour * 3 hours = 150 miles. **

Self-critique (if necessary): OK

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Question: Given average speed and distance moved how do you find the corresponding time interval?

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Your solution: To find the time interval, you would divide the distance moved by the average speed.

Confidence rating: 2/3

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Given Solution: ** time interval = distance / average speed. For example if we travel 100 miles at 50 mph it takes 2 hours--we divide the distance by the speed.

In symbols, if `ds = vAve * `dt then `dt = `ds/vAve.

Also note that (cm/s ) / s = cm/s^2, not sec, whereas cm / (cm/s) = cm * s / cm = s, as appropriate in a calculation of `dt. **

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Self-critique (if necessary): OK

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Question: Given time interval and distance moved how do you get average speed?

Your solution: To get average speed, you divide the distance moved by the time interval.

Confidence rating: 3

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Given Solution: ** Average speed = distance / change in clock time. This is the definition of average speed.

For example if we travel 300 miles in 5 hours we have been traveling at an average speed of 300 miles / 5 hours = 60 miles / hour. **

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&#Very good work. Let me know if you have questions. &#