Unit 4 Mechanical Waves Review

Which picture best represents a sound wave?

• 
• 
• 

Answer explanation

Sound waves are longitudinal. Longitudinal waves move back and forth making areas of compression and rarefaction.

Tags

NGSS.HS-PS4-1

Between which letters is a wavelength?

• A and C

• E and H

• B and F

• C and E

Answer explanation

A wavelength is the distance between two identical parts of a wave. On this picture

A to E,

B to F, and

E to H are all wavelengths.

A to C and C to E are only half wavelengths.

Tags

NGSS.HS-PS4-1

How long did it take this earthquake to reach the recording station?

(each box is 50 seconds)

• 50 s

• 80 s

• 140 s

• 200 s

Answer explanation

The time it takes an earthquake to reach the recording station is measured from the beginning of the seismogram to the p-wave.

What is the time difference between the p- and s-waves?

(each box is 50 seconds)

• 40 s

• 60 s

• 80 s

• 100 s

Answer explanation

The p-wave is the first bit of shaking and the s-wave is the bigger shaking. For this earthquake, the time between these two waves is just over a "box." Therefore, 60 seconds.

Tags

NGSS.HS-PS4-1

If the epicenter is 800 km from the recording station, how fast was the earthquake?

• 8 km/s

• 5.33 km/s

• 0.125 km/s

• 0.188 km/s

Answer explanation

Tags

NGSS.HS-PS4-1

How far away from the epicenter is a recoding station if there is 80 s between the p- and s-wave arrivals?

• 800 km

• 490 km

• 550 km

• 640 km

Answer explanation

Start on the vertical axis at 80 seconds. Then go across until you touch the graph (the black line). Then go down to find the distance. Estimate the distance on the horizontal axis.

Which of the following statements is true for when the air is colder than room temperature?

• Velocity increases

• Frequency decreases

• Frequency increases

• Wavelength decreases

Answer explanation

When the air is colder than room temperature, velocity of sound decreases. Frequency does not change, so wavelength must also decrease.

When does the frequency of a wave change?

• When the medium is different

• When the temperature is different

• When a different note is played

• When the volume is different

Answer explanation

Frequency is not affected by temperature, medium, or volume changes.

Frequency determines the note of sound. Higher frequencies are higher notes and lower frequencies are lower tones.

Tags

NGSS.HS-PS4-1

What is the speed of sound at room temperature?

(Don't forget units!)

Answer explanation

Memorize this value or write it in your notebook!

Speed of sound at room temperature is 343 m/s.

Tags

NGSS.HS-PS4-1

What is the wavelength of the sound made by this tuning fork? The speed of sound is 343 m/s and the frequency of the tuning fork is 512 Hz.

(Round to two decimal places and don't forget units!)

Answer explanation

Tags

NGSS.HS-PS4-1