Assignment1OpenQuery

course PHY 121

6/28 10:20p

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

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

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Your solution:

Get the mean (average) of the set, then get a list of deviations of every number in the set from the mean. Square each deviation. Then, sum the squares. Divide that sum by the total number of items in the list - 1. Take the square root of the resulting number to get the standard deviation.

Confidence Assessment:

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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:

Fitting a straight line to a graph is a matter of simply 'eyeballing' the line that seems to come closest on average to all the data points. You then take some points on your eyeballed line and get a slope and y-intercept which you can use to plug in to the linear formula y = mx + b. Different users could eyeball a different line.

Confidence Assessment: 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:

a velocity is a change in distance over a change in time, which in other words is a rate of change of distance vs. time.

Confidence Assessment: 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):

OK

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

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Your solution:

multiply the two quantities.

Confidence Assessment: 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. **

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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:

Use the formula rAve = `dy/`dt and rearrange algebraically the formula to isolate the `dt or time interval. rAve * `dt = `dy = `dt = `dy/rAve.

Confidence Assessment: 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?

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Your solution:

The velocity formula, again, is rAve = `dy/`dt. In this case the distance moved / time interval.

Confidence Assessment: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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