Question

Walking along the beach, you notice that a new wave reaches the shore every 3.8 s , and you estimate the wave crests to be 2.5 m apart. At what wave speed c are the waves moving?

Answer 1

• The waves are moving at the speed of 0.66 m/s

Step-by-step explanation:

1. Data:

a) period = 3.8 s

b) λ = 2.5 m

c) c = ?

2. Physical principles and formula:

• The time that it takes a wave to complete a cycle is called period. the unit of period is second.

• The period is the inverse of the frequency, i.e. period = 1 / frequency

• The distance between two consecuitve crests is the wavelength

• The equation that relates speed (s), wavelength (λ), and period (T) is:

distance = speed × time

wavelength = speed × T

λ = c × T

meter = (meter/second) × second

m = (m /s) × s

3. Solution:

• λ = c × T ⇒ c = λ / T

• c = 2.5 m / 3.8 s = 0.66 m/s