Physics 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.
We are going to use a somewhat imprecise method for comparing acceleration during free fall. In this lab, we will use multiple masses released simultaneously to determine whether mass affects the rate of descent. In doing this, we have to assume that the forces acting on the masses do not change during their descent, 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.
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.
|Mass||Drop1||Drop2||Drop3||Drop4||Drop5||Mass landing first most often||Conclusion|
|Which lands first?||5kg||Unable to discern difference||2kg||Unable to discern difference||Unable to discern difference||Neither||Masses accelerate at same rate|
Data Collection for crater depth
|Mass||Drop1||Drop2||Drop3||Drop4||Drop5||Average Depth||Standard Deviation|
|Depth Mass #1 (5kg) in cm||2.0||2.3||1.9||2.2||2.6||2.2||0.55cm|
|Depth Mass #2 (2kg) in cm||1.5||1.3||1.7||1.1||1.4|
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 for the 5kg mass is the square root of (1/5) * ((2.2 - 2.0)2 + (2.2 - 2.3)2 + (2.2 - 1.9)2) + (2.2 - 2.2)2 + (2.2 - 2.6)2) = 0.5477. So about 70% of my measurements should be within 0.55cm of the average 2.2, or between 1.7 and 2.7cm -- and they all are. The data above is valid.
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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