Measuring Wave Speed Flashcards

All 5 cards in this deck

State the equation linking wave speed, distance and time, with units.

wave speed (m/s) $=$ distance (m) $\div$ time (s)

What are the steps to measure the speed of sound in air?

e.g. two students standing 100 m apart

1. Measure the distance between them with a tape measure: 100 m.
2. One bangs cymbals; the other starts a stopwatch on seeing the bang and stops on hearing it: about 0.3 s (repeat and mean).
3. $v = x \div t = 100 \div 0.3 \approx 330$ m/s

What are the steps to measure the speed of ripples on a water surface by timing?

e.g. a ripple crossing a tank 0.5 m long

1. Mark a start line and a finish line a measured distance apart: 0.5 m.
2. Time one ripple (wavefront) travelling between them: 1.0 s (repeat and mean).
3. $v = x \div t = 0.5 \div 1.0 = 0.5$ m/s

True or false? Human reaction time is a major source of error when timing sound over a short distance.

True. That is why a long distance is used and the timing is repeated and averaged.

What is the approximate speed of sound in air?

About 330–340 m/s.