Physics Lab Report
How does the length of a string holding a pendulum affect its oscillation?
1. You will need the following apparatus: a pendulum, a piece of string, a clamp, a clamp stand and a timer. 2. Measure out 20cm and attach the metal ball.
3. Establish an angle and let the ball swing for 10 oscillations, timing it and stopping at the 10th one. 4. Write down your results.
5. Repeat steps 2-4 another 2 times so that your results are reliable. 6. Then change the length of the string 4 times, so that you get 5 different sets of results and for each time, repeat it 3 times.
To find the average of the time, I added all 3 values and then divided by three. For example:
(0.89+0.83+0.89)/3 = 0.87
I calculated the absolute uncertainty by considering the furthest point from the mean. For example:
1.31 (mean) – 1.25 (furthest point from the mean) = 0.06
Therefore my absolute uncertainty is +/- 0.06
I calculated the percentage uncertainty by dividing the absolute uncertainty by the mean and multiplying it by 100, like this:
(0.03/1.70) x100 = 0.18%
Source of uncertainties:
The uncertainties in the measurement came primarily from the equipment. Since we used a ruler that was divided into parts of 0.1cm, the readings were normally rounded up or down. The length of string was constant in all 3 times that we repeated each value, however there were uncertainties when had to change the length sizes, as it wasn’t all consistently a 20cm change, there were some 19.5cm or 20.5cm changes as well.
From figure 1 we can see the uncertainties for the relationship between length and time. From the error bars, I could draw the maximum and minimum trend lines. The three lines show the gradients. Steepest line gradient: 0.061(3 d.p.)
Line of best-fit gradient: 0.049 (3 d.p.)
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