2LA_ Lab_3_AccelGravity4

2LA_ - Physics 2LA Acceleration Due To Gravity(contains pre lab assignment This laboratory involves an experimental determination of a value for

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Physics 2LA Acceleration Due To Gravity (contains pre lab assignment**) This laboratory involves an experimental determination of a value for the acceleration due to gravity at the surface of the earth, g . You will: Measure g for different fall distances. Measure g for different falling objects. Consider sources of error, and estimate their influence on the measurement. An emphasis of this experiment is on recognizing and estimating the various uncertainties that contribute to error in measurement. We have learnt about Random (or Statistical) errors and Resolution (or precision) errors in lab 1. Here we will also consider Systematic Errors . Please re read your lab 1 section on error analysis if you are still not comfortable with the concept. Also review the video module on error analysis and significant figures . The pre-lab assignment provides you with practice on calculating and propagating errors. Please turn in the prelab assignment at the start of the lab. Apparatus Free fall apparatus Steel balls Computer with data acquisition interface and analysis software 2-meter stick Precision balance Vernier calipers The Physics For a body starting at rest ( v 0 = 0) falling with a constant acceleration due to gravity, the equation of motion is 2 2 1 gt y =
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where y is the distance (height) the object falls, t is the time of fall, and g is the acceleration of gravity. Sources of Error Experimental error can usually be divided into three broad categories. 1. Random ( Statistical) Error ( Δ ran ): These are errors related to the random errors involved in making the measurements. It is usually be reduced by repeating the act of measurement many times. An example is the measurement of time intervals with clocks where there are errors in starting and stopping the clock, which means that every time you drop something, it takes a slightly different time interval to reach the floor. The value of this error as we saw in lab 1 is given by n ran σ = Δ , where is the standard deviation and n is the number of measurements made. 2. Resolution (Precision) Errors ( Δ res ): This is an error related to the smallest size of length or interval of time that you can measure with the instruments that you are using. For example, we cannot measure distance to better than about 1 mm with the meter stick you will be using. Also, the time interval measurement has a minimum resolution of 0.001s due to the method used. 3. Systematic Errors ( Δ sys ) : These are errors that skew the measurements in one direction due to a imperfection in the equipment or a factor that is neglected in the analysis. For example the wooden meter stick you are using was marked at 90 o F in the factory but is now a slightly different size as the room temperature is 75 o F. Systematic errors are common to all of the measurements, and therefore cannot be reduced by simply repeating the experiment. Other more possible systematic errors in the free fall measurement are: (a) Air resistance.
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This note was uploaded on 09/30/2009 for the course PHYSIC2LA phy taught by Professor Robertclare during the Spring '09 term at UC Riverside.

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2LA_ - Physics 2LA Acceleration Due To Gravity(contains pre lab assignment This laboratory involves an experimental determination of a value for

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