Author: Zach Christoff
Lab Partner: Daniel Baka
Date: 11/13/15
Lab Partner: Daniel Baka
Date: 11/13/15
Purpose
I will investigate Atwood's Device, derive an equation for its acceleration, and compare percent differences of accelerations with different weights.
Theory
The equation with the subscripts (1) represent the forces of the heavier object. The equation with the subscripts (2) represent the forces of the lighter object. The equations below represent how acceleration was derived:
Experimental Technique
To the left is Atwood's device. Two weights are put on each side (left side heavier) and the left side is released from the top.
To measure acceleration, a photogate is placed around the left pulley. The number of revolutions the pulley makes from when the weight is dropped until it hits the table is measured in DataStudio which gives an acceleration in m/s/s. After I had results for calculated and measured accelerations, I compared them using a percent difference formula.
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Data
Analysis
Conclusion
The predicted and measured accelerations % difference vary, depending on the mass. For two masses differing by only 1 gram, the % difference is 27.14%. For two masses differing by 50 grams, the % difference was 4.34%. As the difference in the masses continue to get greater, the % differences get smaller. The major contributors to the differences in acceleration are the friction and steadiness of the string. When the string is let go and the weight falls, friction in the pulleys contribute to the results. For smaller weights with a small difference of mass, friction has more influence than heavier weights with greater mass differences, as reflected by the data. Also, before the string is released, the weights have a tendency to sway. Ideally, it should be released without any motion to get the most accurate results. To reduce the error, I waited until the string was fairly motionless to release it. Also, I aligned the pulleys across from each other, even though there is some parallax error involved. Lastly, since friction was more of a factor for lighter weights with smaller differences, I took measurements that had heavier weights with greater differences.
References
"Atwood Machine." Wikipedia. Wikimedia Foundation. Web. 12 Nov. 2015.
Bowman, Doug. "Atwood's Device Lab." LAHS Phsyics. Weebly. Web. 12 Nov. 2015. <http://lahsphysics.weebly.com/atwoods-device-lab.html>.
Giancoli, Douglas C. Physics: Principles with Applications. 5th ed. Upper Saddle River, N.J.: Prentice Hall, 1998. Print.
Bowman, Doug. "Atwood's Device Lab." LAHS Phsyics. Weebly. Web. 12 Nov. 2015. <http://lahsphysics.weebly.com/atwoods-device-lab.html>.
Giancoli, Douglas C. Physics: Principles with Applications. 5th ed. Upper Saddle River, N.J.: Prentice Hall, 1998. Print.