Question

Difficulty: MediumMeasurement of Time

An experimenter uses a digital stopwatch to record the duration of 4040 complete oscillations of a simple pendulum. The stopwatch displays a reading of 50.8 s50.8\text{ s}, but it has a known positive zero error of +0.8 s+0.8\text{ s}. What is the correct period of oscillation of the pendulum?

  1. 1.25 s1.25\text{ s}Answer
  2. B
    1.29 s1.29\text{ s}
  3. C
    1.27 s1.27\text{ s}
  4. D
    0.80 s0.80\text{ s}

Answer

The correct period of oscillation is 1.25 s1.25\text{ s}.
To find the true duration of the oscillations, the positive zero error of +0.8 s+0.8\text{ s} must be subtracted from the stopwatch display of 50.8 s50.8\text{ s}, giving an actual elapsed time of 50.0 s50.0\text{ s}. Dividing this corrected time by the 4040 complete oscillations gives T=50.0 s/40=1.25 sT = 50.0\text{ s} / 40 = 1.25\text{ s}.

Step-by-Step Solution

1
Calculate the true time interval by correcting for the instrument zero error.
tactual=50.8 s0.8 s=50.0 st_{\text{actual}} = 50.8\text{ s} - 0.8\text{ s} = 50.0\text{ s}
A positive zero error means the timer reads higher than the true time, so the error value must be subtracted.
2
Calculate the period of a single oscillation by dividing the total corrected time by the number of oscillations.
T=tactualN=50.0 s40=1.25 sT = \frac{t_{\text{actual}}}{N} = \frac{50.0\text{ s}}{40} = 1.25\text{ s}
The period TT is defined as the time required to complete one full oscillation cycle.

Key Concept

Measurement of Time with Zero Error Correction
Estimated Time:1m 30s
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