Measuring the Speed of Waves Flashcards

All 5 cards in this deck

Which equation gives wave speed from a measured distance and time?

$\text{speed} = \dfrac{\text{distance}}{\text{time}}$

What are the steps to measure the speed of sound in air?
e.g. two students standing 100 m apart, one banging cymbals

1. Measure the distance between them with a tape measure: 100 m
2. Time from seeing the cymbals hit to hearing the sound, repeating and taking a mean: about 0.30 s
3. speed $=\dfrac{100}{0.30}\approx 330$ m/s

What are the steps to measure the speed of ripples on a water surface without measuring the wavelength?
e.g. a ripple crossing a tank

1. Measure the distance the wave travels (the length of the tank) with a metre rule: 0.60 m
2. Time the wave to travel that distance with a stopwatch: 1.5 s
3. speed $=\dfrac{0.60}{1.5} = 0.40$ m/s

True or false? The speed of sound in air is about 330 m/s.

True. Accepted values are roughly 330–340 m/s.

Why are the timings repeated and a mean taken when measuring the speed of sound in air?

To reduce the effect of random errors, mainly human reaction time when starting and stopping the timer.