IB Physics Internal Assessment
In this internal assessment, I am given a cantilever to find the physical properties of it. I decide to investigate the relationship between the force I act on one side of the cantilever and the maximum acceleration the tail can reach. This experiment will be also showing the elasticity of the cantilever. Since I pull down one side of it and fixed the other side, when I cut the string, it will bounce up and down until all the internal energy is depleted. Text books
1) A piece of cantilever that is made by acrylic plastic (length:35.2cm±0.1; Width:4.0cm±0.1; thickness:0.2cm±0.1) 2) An accelerometer (sensor; least count: 0.01ms^-2)
3) An Newton meter (the indicator points to 0 when it is hanging upside down; the least count is 0.25N; Measurement Range: 0N~5N) 4) String (length: 2cm *30)
5) 3 heavy texts book
6) A computer that has Logger Pro
1) Set up the experiment as the graph shows
2) Connect the accelerometer with the computer
3) Adjust the sensor to zero when the cantilever is at the equilibrium 4) Adjust the indicator of Newton meter to zero when it is hanging upside down 5) Tie the string at the tail of the cantilever, hang the Newton meter to the other side of the string 6) Pull down the Newton meter, try to keep in the same position before cut the string 7) Cut the string
8) Collect the data that are created by computer
9) Redo (3)~(8) 2 more times for each test point
The dependent variable of my experiment is the maximum acceleration that the tail of the cantilever can reach. In the data process, I set this variable as the Y value. This variable is measured in meters per second square (m/s^2). Because the tail will bounce up and down, I will have both positive and negative values for acceleration. Having only one maximum acceleration value, I will probably not obtain the accurate information from the final result, because if the tension force is too big, the bounced back force might upspring the text books, then the data would not be precise. Hence I am going to collect not only the positive maximum values, but also the minimum values (I will written as “negative maximum value” in the rest of this IA) of the acceleration. Independent Variable
The independent variable of my experiment is the force I act on the tail of the cantilever. I pick ten different values (from 0.75 to 3.0, where increases by 0.25 for each test point) for it and it is measured in Newton (N). In the graph, this will be shown as the Y value. The capacity of the force will affect the maximum acceleration. Controlled Variable
There are several variables that need to be controlled in this experiment. First of all, the length of the part of the cantilever that I extend out of the table must be kept in the same. I choose the midpoint of the cantilever to fasten on the table and the length of the overhang is to be half of which of the cantilever in each trial. Second of all, the total amount of weight that was put on the cantilever so that the cantilever would be suppressed must be the same. Here, I put 4 heavy science text books on top of the cantilever during the whole experiment. Thirdly, the length of the string that is used for hanging the Newton meter has to be approximate the same for each trial. At last, the Newton meter that I have been using during the whole experiment is always the same one.
I presume that the relationship between the force which I act on the tail of the cantilever, and the maximum acceleration the tail can reach, will be either inverse proportion or logarithmic or exponential. The reason of making this hypothesis is all of these three relationship have a common ground—a horizontal asymptote. And my living knowledge tells me that once the cantilever reaches its extremity, it cannot be bended any...
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