Lab
Measuring Time and Gravity with a Pendulum
Anna, this is to HELP you. It took me a long time so I hope it does some good. Don't copy my crap (I know you wouldn't lol) but just learn from it. The graphs are kind of hard to do but eventually you figure out what intervals to use etc...
Sorry for thinking yours wasn't due...your lab schedule is different from mine.
First table, under Procedure - Your numbers will differ because well because they will :) However, the basic idea is the same.
The elapsed time- You should have gotten these numbers in class with the experiment
Time per 10 Cycle Interval- This is the difference between the different cycles. See below.
Average Period Within Each Interval (T)- This is the elapsed time divided by the number of elapsed cycles
Sample Table
| Number of Elapsed Cycles | Elapsed Time (s) | Time per 10 Cycle Interval | Average Period within Each Interval |
| 10 | 17.72 | 17.72 (17.72) | 1.772 (17.72 / 10 cycles) |
| 20 | 35.66 | 17.84 (35.66 - 17.72) | 1.783 (35.66 / 20 cycles) |
Remember, YOUR CALCULATIONS WILL BE DIFFERENT!!!
Second table (the one using different bobs - such as brass, wood, etc)
Sample Table
| Mass, M (Kg) *Remember! The scale used in class is in grams so you have to divide by 1000* | Time per 20 cycles | Average Period (T) |
| Wood .0115 | 26.57 | 1.772 (17.72 / 10 cycles) |
| Aluminum .0278 | 28.01 | 1.783 (35.66 / 20 cycles) |
The mass- Mass of different weights...weighed in class
Time per 20 Cycles- Found in class
Average Period Within Each Interval (T)- Time divided by 20 (the number of cycles)
Remember, YOUR CALCULATIONS WILL BE DIFFERENT!!!
Third table (the one adjusting the length)
Sample Table
| Length (m) | Square root of L | Time for 20 cycles (s) | T (s) |
| .700 | .84 | 33.81 | 1.69 (33.81 / 20 cycles) |
| .600 | .78 | 31.45 | 1.57 (31.45 / 20 cycles) |
The length- Already given
Square root of l- The square root of the first column
Time for 20 Cycles- measured in class
T- time for 20 cycles divided by 20
Remember, YOUR CALCULATIONS WILL BE DIFFERENT!!!
Questions
Is the motion of the pendulum periodic? Explain.
Yes, the motion of the pendulum is periodic because the average periods for the experiments (where variable changes - mass, length, and number of elapsed cycles) are all the same. Although they do differ slightly, this is caused by human error and outside uncontrollable factors.
Does the period of the pendulum depend on the mass of the bob?
The period of the pendulum does differ slightly with the mass of the bob. The lab showed that the heavier bobs had longer periods.
Calculations
Find the slope of the line in the last graph (T versus square root L) This slope will be M.
The value of the local gravity at BTHS will be G.
g = 4 pie squared / m squared
g = 4 pie squared / 4
You have to work out 4 times pie and then divide it by your slope squared.
g = 9.87
Yay it works!!!!
Remember, YOUR CALCULATIONS WILL BE DIFFERENT!!!
Graphs
The first graph is period (T) versus mass (M). From this table:
|
Mass, M (Kg) *Remember! The scale used in class is in grams so you have to divide by 1000* This will be on x axis |
Time per 20 cycles | Average Period (T)
This will be on y axis
|
| Wood .0115 | 26.57 | 1.772 (17.72 / 10 cycles) |
| Aluminum .0278 | 28.01 | 1.783 (35.66 / 20 cycles) |
The second graph is period (T) versus square root of L (M). From this table:
| Length (m) | Square root of L
This will be on x axis |
Time for 20 cycles (s) | T (s)
This will be on y axis |
| .700 | .84 | 33.81 | 1.69 (33.81 / 20 cycles) |
| .600 | .78 | 31.45 | 1.57 (31.45 / 20 cycles) |
That's all folks!!
