Passage III

Two students were each asked to experimentally determine the speed of sound in air, sa. For the atmospheric conditions in which their experiments were performed, the correct value of was sa 347.1 m/sec.

Experiment 1

Student 1 placed a horn, which could emit a short pulse of sound waves, at a distance x, in m, from a tall cliff (see Figure 1).

He started a stopwatch when he heard the horn emit a sound pulse and stopped the stopwatch when he heard an echo return from the cliff. He recorded this time interval, Δt1, in sec, and then calculated sa, using the equation

Student 1 performed 3 trials at each of 3 values of x, averaging the sa results at each value of x (see Table 1).

Experiment 2

Student 2 placed the horn and 2 microphones—M1 and M2—in a straight line such that the microphones were separated by a distance y. She then connected a timer to both microphones (see Figure 2).

She set the timer to start when the first microphone detected a sound pulse and to stop when the second microphone detected a sound pulse. She recorded this time interval, Δt2, and then calculated sa using the equation

Student 2 performed 3 trials at each of 3 values of y, averaging the sa results at each value of y (see Table 2).

16. Student 1 plotted the △t1 data versus x and then graphed a line of best fit to the data, as shown below.

The gap shown near the bottom of the vertical axis suggests that even if the value of x had been 0 m, the value of △t1 would not have been 0 sec, as one might expect. Based on the description of Experiment 1, this gap was most likely the result of:

Answer and Explanation

Your Answer is

Correct Answer is F

Explanation

General knowledge questions.

The obvious flaw in the design of Experiment 1 is that it relies on human hearing and reaction to time, which is prone to very large errors, because people need reaction time when timing, which will cause the recorded time to change. Long, the calculated speed of sound becomes smaller