Chapter 25, Problem 40A

If a wave vibrates up and down twice each second and travels a distance of 20 m each second, what is its frequency? Its wave speed? (Why is this question best answered by careful reading of the question rather than searching for a formula?)

To determine

Frequency of a wave vibrates up and down twice each second.

Answer to Problem 40A

Frequency of the wave is $2\text{ Hz}$ .

Explanation of Solution

Given:A wave vibrates up and down twice in a second. The wave travels $20\text{}\text{m}$ in a second.

Formula Used:Frequency $\nu$ is equal to the number of cycles per second as

  $\text{v = Number of cycles traveled per second}$

Calculation: When a wave vibrates once up and down then it completes a cycle. Frequency of a wave is calculated as the number of cycles traveled in a second. Here, a wave vibrates up and down twice in a second i.e. it completes 2 cycles in a second. Thus, the frequency of the wave is $2\text{ Hz}$

Conclusion: Thus, frequency of the wave is $2\text{ Hz}$

To determine

Speed of the wave vibrating up and down twice each second. This question is best answered by a careful reading of the question rather than searching for a formula.

Answer to Problem 40A

The wave speed is $20\text{ m/s}$ . It requires a basic understanding of reading comprehension and physics knowledge despite searching for formula only.

Explanation of Solution

Given: A wave vibrates up and down twice in a second. Wave travels $20\text{}\text{m}$ in a second.

Formula Used:Speed of sound wave is calculated as

  $\text{speed = distance/ time}$

Calculation: Since a wave travels $20\text{}\text{m}$ in the given time interval of a second. Thus, the speed of the sound wave is $20\text{ m/s}$ .

Since, to find the answers to the given problem no just direct formulas are necessary. But, basic physics knowledge with clear reading comprehension is also required to understand the concept.

Conclusion: Thus, the wave speed is $20\text{ m/s}$ . It requires a basic understanding of reading comprehension and physics knowledge in spite of searching of formula only.