Physis Honors Lab
Note: The two labs, Falling Bodies 1 and Falling Bodies 2, are similar in methods and the lab instructions may appear to be identical, but this isn't the case! The two labs have very different goals and important differences in procedure. Pay attention to the details in the instructions.
Uniform motion in one dimention, whether or not it is under constant velocity, is difficult to observe carefully. You must be able to mark the position of the falling object without actually affecting the motion of the object, so somewhat more sophisticated lab equipment is required than you usually find around the house.
In a standard AP class or freshman college physics lab, you would perform experiments and record the position with respect to time of a little metal cart on an air track. You may wish to review the YouTube video One Dimension - Constant Velocity and Constant Acceleration (NPS Physics) to get an idea of how an air track works.
We are going to use a less precise method of determining acceleration during free fall. Rather than try to determine the position of our falling body at successive seconds during a single fall, we are going to vary the drop distance and time the body's descent multiple times. In doing this, we have to assume that the forces acting on the ball do not change, and that we can keep from introducing factors (differences in air friction, changes in mass, changes in horizontal velocity) which might cause the motion to vary from one drop to the next.
You are at liberty to use any other means to measure the vertical distance; this is only a suggestion.
Arrange your data as you perform the reduction in some neat order, so that it is easy to see and understand what you have done. You may want to consider setting up a spreadsheet and letting it do the calculations for you. Here is a suggestion, but you can improve on it.
You will also need to determine the accuracy of your measurements. Physicists use a statistical method called determination of the standard deviation. According to this theory, 68.3% of all repeated measurments should fall within the standard deviation (plus or minus) from the average.
In the table above, the standard deviation at 20m is the square root of (1/3) * ((2.17 -2.2)2 + (2.2-2.17)2 + (2.2-2.17)2) = .0577 ~ .06. So about 70% of my measurements should be within .06 sec of the average 2.167--which they are.
Your report should include:
Follow the instructions at the Moodle to post your lab reports where your fellow students can find them.
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