Assignment 1

course Phy 201

ñϥz^zlyassignment #001

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001.

Physics I

01-20-2008

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20:51:52

Explain in your own words how the standard deviation of a set of numbers is calculuated.

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RESPONSE -->

The standard diviation is simply the square root of a variable from a set of intervals or sample of numbers.

confidence assessment: 1

Standard deivation is actually the square root of an average of the deviations from the mean. Recall how the standard deviation was calculated:

You calculated the mean of the n results.

You found the deviation of each result from the mean.

You squared the deviations.

You added up the squared deviations and 'averaged' them, dividing by n - 1 if n is less than 30.

You took the square root of the result.

Recall also that the standard deviation differs from the mean of the deviations, but usually the difference is not great, tending to run around 20% or so for most data sets.

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20:54:04

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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RESPONSE -->

Fitting a line to a set of data points can be tricky since none of the points can be touching the straight line. It is uncertain to know how far off you may be from the actual y intercept when approximating the points. One person may use a line going one direction, while someone else may use a line going in the opposite direction which would give you two different slopes and intercepts.

confidence assessment: 2

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20:57:05

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

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RESPONSE -->

Velocity is the dispacement/elapsed time which is how fast is an object going and which direction is it moving in. Velocity is changing thefore it is an example of a rate. THe key to velocity is displacement not the total distance traveled as in speed.

confidence assessment: 2

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20:57:44

** 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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RESPONSE -->

Velocity=final position-Initial position/Time

self critique assessment: 3

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20:58:08

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

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RESPONSE -->

average speed =distance/time

confidence assessment: 3

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20:59:16

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

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

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RESPONSE -->

50/1*3=150

self critique assessment: 3

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21:00:50

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

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RESPONSE -->

Time interval is found by subtracting one time from another for a given oberserved period.

confidence assessment: 3

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21:01:42

** 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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RESPONSE -->

100/50=2 (understood)

self critique assessment: 3

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21:02:24

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

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RESPONSE -->

Average speed =distance/time

confidence assessment: 3

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21:03:29

** 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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RESPONSE -->

300/5=60 m/h

self critique assessment: 3

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