Quick Lab: Tuning Fork Interference

Name: Partners:

*** This set of mini labs is designed to be COMPLETED IN CLASS and HANDED IN AT END OF CLASS. You may use your textbook or phone to help with answers as well. Work in a team and submit one set of answers. However, you will most likely want to each have a copy as these are possible test questions. EXPLAIN IN DETAIL USING PHYSICS TERMS.

Part 1: Quick Lab: Natural Frequency

Materials: 3 bottles water Procedure:

1. Fill each bottle with different amounts of water. 2. Blow over the top of each bottle until it makes a clear sound (single note or as close as possible). Questions: 1. The bottle with the most water makes the (highest or lowest) ______sound. This is because …

Part 2: Quick Lab: Tuning Fork Interference

Materials: 2 Tuning forks (256 Hz) mallet clay 1 other tuning fork (at least 10 Hz lower or higher than 256 – the further apart in frequencies the better)

Procedure: 2. Predict: If the tuning fork has a different frequency, what should change?

3. Strike the 256 tuning fork with a mallet. Listen and then stop the vibration. Strike the other 256 tuning fork in the same way. Do the 2 tuning forks sound the same or different? Why?

4. Strike the two tuning forks together at same time. Listen for at least 10 seconds. Describe what you hear, and how it differs (if it differs) from the sound of a single tuning fork. Why?

5. Choose another tuning fork with a frequency of at least 10 Hz higher or lower than 256 Hz. Strike this fork first. Then strike the 256 Hz tuning fork after. What do you notice about these two sounds? Why? 6. Now strike the “other” tuning fork and the 256 Hz tuning fork at the same time. Describe what you hear. How is it different from the sound of the two tuning forks with the same frequency? Why?

7. Now put some clay on the end of one of the 256 Hz tuning forks. This should change the frequency by about 5 Hz. Predict what will happen when you strike the original 256 Hz fork and the clay altered fork at the same time.

8. Now actually strike the clay fork and the 256 Hz fork at the same time. Did your prediction happen? Explain why or why not.

9. Now strike the 256 Hz fork and put the single end on the lab bench. What happens? What if you do it with the other forks?

CONCLUSION: The higher the frequency, the ______(higher or lower) the sound.

Part 3: Quick Lab: Speed of Waves

Materials: Long coil Stopwatch (phone) Metre stick

Procedure: *** For this section, make sure you do not change the distance (and therefore tension) in your spring!!!

10. Produce a small single TRANSVERSE pulse and record the time it takes from when the pulse is produced to when it gets to your partner and back to you (so two trips along the spring). Also measure the distance for this to happen. (Sit on the ground to do this). Repeat with medium and large waves. Record your information in the table below.

Data Table 1: Speed of Waves

Size of Wave Distance between you and Time it takes for a Speed of Wave partner x 2 in metres single pulse to get back (should stay the same) to you in seconds Small

Medium

Large 11. What conclusion can you make about the speed of ANY SIZE PULSE that moves through the same medium?

12. Send multiple transverse waves from one end of the coil at a slow, constant frequency. Then send multiple waves from the same end of the coil at a faster, constant frequency. Observe and describe what happens when you vary the rate (frequency) at which your hand moves or vibrates.

13. Send multiple longitudinal waves from one end of the coil at a slow, constant frequency. Then send multiple waves at a faster, constant frequency. Observe and describe what happens when you change to longitudinal waves.

Part 4: Quick Lab: Interference of Pulses Materials: Long coil Procedure:

14. Have 2 people hold the slinky above the floor. Produce a transverse pulse (going horizontal not vertical) from each end AT THE SAME TIME. Try to make the slinky’s waves interfere CONSTRUCTIVELY. a) Draw and label a diagram of the two pulses just before they meet each other.

b) Draw and label a diagram of the two pulses when they meet each other in the middle.

c) Draw and label a diagram of the two pulses just after they meet each other.

\\\\ 15. Complete the same exercise as in procedure 14 but make the slinky’s waves interfere DESTRUCTIVELY. a) Draw and label a diagram of the two pulses just before they meet each other.

b) Draw and label a diagram of the two pulses when they meet each other in the middle.

c) Draw and label a diagram of the two pulses just after they meet each other.

Part 5: Quick Lab: Boundaries

Materials: Long coil tape string

Procedure:

16. Produce a transverse pulse while your partner firmly grips the other end of the slinky, causing a boundary to occur. a) What type of boundary is your hand? ______

b) When the pulse REFLECTS from this boundary, what happens to the reflected pulse?

17. Measure about 2m of string. Attach to the coil with tape. Produce a transverse pulse while your partner firmly grips the other end of the slinky, causing a boundary to occur where the spring meets the string. a) What type of boundary is your hand? ______

b) When the pulse REFLECTS from this boundary, what happens to the reflected pulse? Part 4: Standing Wave

16. Watch the following video on youtube: https://www.youtube.com/watch?v=-gr7KmTOrx0 (or you can youtube Standing Wave Demo). Try to create this standing wave using the drill. One person should use the drill while the other should hold the end of the string. Can you create a standing wave? How many nodes does it have? Can you create another standing wave with more or less nodes?

CONCLUSION: On our google classroom, post your response to one of these questions. You can also post errors and questions about this lab. Part 4: Speed of Sound

Materials: PVC piping (tube) ruler tuning fork water Graduated cylinder (500 mL)

1. Tuning Fork Frequency: ______

2. Inside Diameter of PVC piping: ______

3. Put water in your graduated cylinder. Place the tube in the graduated cylinder. Length of column of air (top of PVC ): ______