Waves moving on a lake have a speed of 2.8 m/s and a distance of 1.1 m between adjacent crests. (a) What is the frequency of the waves? Hz

Question

(b) Find the period of the wave motion.

s

Answer 1

While I can not answer your homework or test questions, perhaps I can help you to understand how to solve these problems.

First, you need to have a clear picture of the anatomy of a waveform. You can luck up a waveform diagram online.

Waveforms are repeating events over time. They occur in cycles which are repetitions of the same or similar motion.

In a waveform, these repeating events are crests and troughs centered around a line. The line represents the “zero” state and. So, the waveform travels from zero upward to a peak or “crest” and then falls down toward zero. The waveform passes downward through zero and reaches its lowest point “trough” then begins its upward movement toward zero.

When a waveform completes its movement first up from zero to crest, then down below zero to trough, then back to zero, that’s a complete cycle.  

Wavelength is the distance covered in a complete cycle. 

Period is the time it takes to complete a cycle.

Frequency is the number of complete cycles per second completed.

Once you understand these concepts, then you can look at the problem and determine:

·        What information does it give you?

·        What is it asking?

The problem gives you:

·        Wavelength = 1.1m (wavelength is defined as the distance between consecutive corresponding points of a waveform) The problem says “a distance of 1.1m between adjacent crests.”

·        Wave velosity = 2.8 m/s

The problem asks you for:

·        Wave Frequency (Hz)

·        Wave Period (s)

Formulas:

Frequency   =    Velocity/Wavelength or  f = v/λ Units of frequency are hertz (Hz) cycles per second

Wave Period = 1/frequency                 or  T = 1/f Units of the period are  seconds  (s)

Or you could use

Wave period = Wavelength/Velocity  or T = λ/v

Where: 

f = frequency

λ = wavelength

v= velocity

T = period

Summary:

·        Know and understand waveform anatomy (see attached illustration)

·        Read the question and determine what information it gives you, and what information it is asking for.

Break it down and write it out.

·        Determine the appropriate formula(s) required.

·        Plug in the numbers and solve for what the problem is asking for.

The biggest thing about these problems are Knowing the waveform anatomy & terms, Knowing the appropriate formula, Working the math.

Good luck and have fun,

You can do this.