Open Query 1

course Phy 201

2/10/10 9:15 pm

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

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Your solution:

To find the standard deviation of a set of numbers we first must find their mean. From here we find each numbers deviation from the mean. The next step is to find the average of the deviations, done by squaring each deviation, adding those answers together and dividing by one less than the number of data points. From here we find the square root of the average, and we have the standard deviation of a set.

confidence rating #$&*: 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 y vs. x data, we estimate a line of best-fit. To find a line of best-fit we estimate a straight line that is most likely to minimize the squared deviations of the points. It is highly unlikely that the line will intersect any of the given data points. After we have estimated the line of best-fit, we need to name two points on the line to determine its slope, and we need to estimate where it is likely to cross the y-axis to determine its y-intercept.

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.

Your solution:

Velocity to me means the speed at which an object moves over a chosen distance. I believe it is an example of a rate, because we are comparing two data groups, distance and time.

confidence rating #$&*: 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. **

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:

If we are given an average speed and time interval, we can multiply the two to find the distance traveled.

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. **

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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:

If we are given an average speed and the distance traveled, we can divide the distance by the average speed, to get the time interval.

confidence rating #$&*: 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:

Given a time interval and traveled distance, we can divide the distance by the time interval to get the average speed.

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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&#This looks good. Let me know if you have any questions. &#