![]() What is the relationship between the speed of sound (c), c v s, and the ratio f / f s? 4. Analyze: Compare the first, third, and fifth columns of the table. Speed of sound (c) Velocity of source (v s ) c v s Observed frequency (f) f / f s 240 m/s 60 m/s 240 m/s 80 m/s 240 m/s 120 m/s 240 m/s 160 m/s 240 m/s 180 m/s 3. This value represents the magnitude of the Doppler shift. Divide each observed frequency by the source frequency (f s = 1,000 Hz) to complete the table. Next, use the Gizmo to measure the observed frequencies (f). Gather data: Subtract the velocity of the source (v s ) from the speed of sound (c) to fill in the third column of the table. What is the frequency of the sound waves hitting the observer? 2. Click Play, and then click Pause when sound waves are striking the observer. Measure: Place the observer in the middle of the road so he is directly in front of the car. Question: How can you use the Doppler shift to measure the velocity of an object moving towards an observer? 1. In the Doppler Shift Advanced Gizmo, each red ring represents 1,000 sound waves. The observed frequency (f ) is equal to the number of waves passing the observer each second. The source frequency (f s ) is equal to the frequency of waves emanating from a moving source of sound. Introduction: Waves are described by their frequency, or number of cycles per second. Turn on the Observed frequency (Hz) checkbox. Set the frequency (f source ) to 1,000 Hz, the velocity of the source (v source ) to 60 m/s and the speed of sound (v sound ) to 240 m/s. How will the sound of the car change as the car passes the observer?ΔΆ Activity A: Source moving towards observer Get the Gizmo ready: Click Reset ( ). How does the distance between sound waves compare in front of and behind the car? 2. ![]() On the Gizmo, check that v observer is 0 m/s, f source is 500 Hz, v source is 100 m/s, and v sound is 340 m/s, close to the velocity of sound in air. With the Doppler Shift Advanced Gizmo, you will investigate how the speed of the moving object is related to the magnitude of the Doppler shift. How can you tell? Gizmo Warm-up The change in pitch an observer hears as an object passes by is an example of the Doppler shift. Which observer hears the highest pitch (tone)? Which observer hears the lowest pitch? 2. 1 Name: Date: Student Exploration: Doppler Shift Advanced Vocabulary: Doppler shift, frequency, pitch, radar gun Prior Knowledge Questions (Do these BEFORE using the Gizmo.) The image at right shows two observers watching a car pass by.
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