Jae Yoo
8/31/16
partners: John Demontano, Shawn Mazzio
Accomplishment
determination of g(and learning a bit about Excel) and some statistics for analyzing data
Theory/Introduction
In the absence of all other external forces except gravity, a falling body will accelerate at 9.8m/s^2
Apparatus/Procedure
1. Pull a piece of paper tape between the vertical wire and the vertical post of the device. Clip it with a weight to keep the paper "tight"
2. Turn the dial hooked up to the electromagnet up a bit
3. Hang the wooden cylinder with the metal ring around it
4. Turn on the power on the sparker thing
5. Hold down the spark button on the sparker box
6. Turn the electromagnet off so that the thing falls
7. Turn off power to the sparker thing
8. Tear off the paper strip
Data
The film of paper had dots generated by sparks that we measured with a ruler. Each dot was 1/60th of a second apart from one another. Dots gets more spread apart as we measure the distance between two dots.
Calculated results/graphs of data
We logged our time, distance, delta x, mid-interval time and mid-interval speed onto excel. With excel we are able to use the program to calculate and input the data in a timely manner. In the time column A3 we entered =A2+1/60 and then dragged the corresponding cells to have excel input the numbers for us. For distance the data was from the paper film we measured. Delta x the formula was =(B3-B2). Mid-interval time was =A2+1/120. Mid-interval speed was =C2/(1/60).
Velocity vs Time
Graphing our speed versus time, we highlighted our data from columns D and E. Selecting the XY scatter graph we were able to obtain what is showing on the left. Using excel to graph our data also allowed us to gain our slope by adding a trend-line in the options.
Mid-interval is the point between each of the 1/60th of a second.
Position vs Time
We obtained the position over time graph the same way as above. The difference is we highlighted our data from column A and B.
Analysis
We can find gravity from both the graphs by using two kinematic equations
we can apply first equations from velocity vs time graph to find g
or we can apply 3rd equation to find g from position vs time graph
Conclusions
We got g = 9.53m/s^2 and 9.58m/s^2 as the result from both data, y=952.89x+65.886 and y=479.18x^2+64.882x+0.0669
These are very close from the actual value of g=9.8m/s^2
There are some uncertainties during the lab and we will be dealing with it at part 2
Part 2- Uncertainty
There are two forms of error, random error and systematic error
Random error is scatter in data that you can't 'blame' on anything particular
Systematic error comes from assumptions we've made which are not true. We need better and more expensive equipment to solve the problem
Other error is human error, mistakes from human
Standard Deviation is a quantity calculated to indicate the extent of deviation for a group as a whole.
So we found Standard Deviation of the Mean of the class' data to find our uncertainty of g
As the result, we got 935.9+/-28.27 as our g
All of our g's are lower than the actual g
our average value is also lower than accepted value of g
Class's values of g is also lower than actual g
There are both systematic errors and random errors on our data
The lab was to find g and learning about uncertainty. There were errors occurred due to air resistance and friction forces. Key ideas for the lab was to know how to use excel and find g from the graph. we were supposed to get lower g value than the actual due to errors and be able to find the uncertainties from the errors.
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