Physics 121 General Physics
Concept Quizzes
Chapter 18 Superposition and Standing Waves

The figure shows a standing wave. Each colour shows the string at a different instant in time. The string vibrates between the extremes a and e. Let upward motion correspond to positive velocities.

1. At the instant when the string looks like c (purple) the instantaneous velocity of points along the string

	is zero everywhere.
	is positive everywhere.
	in negative everywhere.
	depends on location along the string.

2. When the string look like e (blue), the instantanous velocity of points along the string is

	is zero everywhere.
	is positive everywhere.
	is negative everywhere.
	depends on location along the string.

The traces below show beats that occur when two different pairs of waves are added.

Pair 1:
Pair 2:

1. For which of the two pairs is the difference in frequency between the original waves the greatest?

	Pair 1.
	Pair 2.
	Same for both pairs.
	Need nore information.

2. Which of the two pairs of original waves contains the wave with the highest freqency?

	Pair 1.
	Pair 2.
	Same for both pairs.
	Need nore information.