\fPHY1025L Lab #3 Human Reaction Time Lab OBJECTIVE: To determine the reaction time of a Human being. INTRODUCTION: If a student lets a ruler go, it will begin to fall with an initial velocity of 0 m/s and with a constant acceleration of 9.80 m/sz. Because the acceleration is constant, the ruler's velocity will increase proportionally to the elapsed time and so the ruler's displacement will increase at an increasing time dependent rate. If a second student attempts to grab the falling ruler as soon as they see it begin to fall, then the ruler's displacement is related to that person's reaction time (because the time the ruler spends falling is eaual to the reaction time of the nersonl. Fi 1. Schematic Dia ram of Procedure Below, one student releases a ruler and the other catches it. Releaser Releaser Start Finish Before release, the students need carefully note the position of the catcher's fingers relative to the meter stick. After the catch, the students need to note the exact point on the meter stick where the catch is made. The difference between the two positions is the start-to-finish displacement (Ax) The start-to-finish displacement is related to the reaction time. \fEquation 1 can be solved for t, the time the ruler falls which is equal to the reaction time if Ax (the displacement) is known. The quantity we will attempt to measure is the displacement (Ax). How can we get a good measure of the uncertainty in our measurement of the reaction time? We could use the uncertainty in measurement of the ruler to find the lowest, the average and the highest displacement, but this ignores variation in human reaction times. In a case such as ours, it's better to use a statistical measure of scatter such as the \"standard deviation" to estimate the uncertainty. The equation for the standard deviation (0) is given by: _ E .2 Q'X: \\I1T2(Xi_x)2 q Where: ox = the standard deviation N = the number of measurements (i.e., no. of trials) Xi = the value of each measurement from 1 to i Y: the average value of the displacement ( Note: xi and E are the) same as Axi and AE. The equation for the standard deviation can be rewritten as: Some Rules of Measurement: A. When the measuring tool is crude compared to the thing to be measured, measure only once. But carefully! B. If the measuring tool is fine compared Bell Curve Distribution to the thing to be measured, measure Mean multiple times and use statistics. The more measurements, the more \"Bell\" Number shaped the distribution should become. Measured Quantity PROCEDURE: 1. 2. Practice releasing and catching a few times to make sure you'll get the fastest and most accurate times possible. Carefully note XINITAL. Because any one trial can have issues, do 5 trials and use the average displacement in your calculation. [Note: AX will be negative (because the ruler is moving in a negative direction).] . Using AXAvERAoE, solve eq. 1 for t& calculate your average reaction time. . Calculate the standard deviation (0) to get the uncertainty in Ax. DATA DATA TABLE 1