# Waves, Sound and Light: Wave Basics

## Wave Basics: Audio Guided Solution

#### Problem 20:

In the Standing Wave Lab, lab partners Chloe and Paige adjust the frequency of a mechanical oscillator in order to vibrate a 1.38 m length of elastic cord at one of its harmonic frequencies. The cord vibrates with the pattern shown below when the frequency is set to 79.4 Hz. Determine the speed of the waves in the elastic cord.

## Habits of an Effective Problem Solver

• Read the problem carefully and develop a mental picture of the physical situation. If necessary, sketch a simple diagram of the physical situation to help you visualize it.
• Identify the known and unknown quantities and record in an organized manner, often times they can be recorded on the diagram itself. Equate given values to the symbols used to represent the corresponding quantity (e.g., v = 12.8 m/s, λ = 4.52 m, f = ???).
• Use physics formulas and conceptual reasoning to plot a strategy for solving for the unknown quantity.
• Identify the appropriate formula(s) to use.
• Perform substitutions and algebraic manipulations in order to solve for the unknown quantity.