Lab report

Experiment 1: Waves

In this experiment, you will use a Slinky® to model transverse and longitudinal waves and calculate the speed of a wave.

	Materials 1 Slinky® Masking Tape 5 N Spring Scale Stopwatch Tape Measure	*Willing Participant *You Must Provide

Procedure

Transverse Wave Speed vs. Longitudinal Wave Speed on a Slinky®

1. Find an open area with a flat, smooth floor.

2. Use the tape measure to measure out a two meter length, making it as straight as possible. Use the masking tape to mark the zero meter and two meter distances.

3. Give one end of the Slinky® to your partner and stretch it on the ground along the marked two meter distance. Try to hold as few of the coils at the end of the Slinky® as possible. Note: If a partner is not available, try tying this last coil of the Slinky® to a table chair leg. It is important to tie the slinky as tight as possible to the leg.

4. While holding the Slinky®, quickly make a motion perpendicular to the Slinky®, sending one transverse wave down the length of the Slinky®. Make sure your partner keeps the other end still.

5. Try sending waves of different sizes, and vary how quickly you move your hand to send the pulse. Keep a mental note of how fast the waves seem to go.

6. Try sending one longitudinal wave down the slinky. Keeping the Slinky® ends in one place, grab several coils more than what you are holding onto and stretch them toward you. Let go of the extra coils, but make sure to keep holding on to the end. You can also make waves by quickly pushing your end forward and pulling back.

Speed of Transverse Waves on a Slinky®

1. Use the 5 N spring scale to determine the mass of the Slinky® . Record the mass in Table 1.

2. Count the number of loops the slinky contains. Record this number in Table 1.

3. Use the distance marks for Procedure 1 and give one end of the Slinky® to your partner and stretch it on the ground along the marked two meter distance. Try to hold as few of the coils at the end of the Slinky® as possible.

4. Use the stopwatch to measure the time it takes for one transverse wave to return after you send it down the Slinky® . Record the time it takes to make one round trip in Table 2.

5. Repeat Step 4 four more times.

6. After your last trial, take the spring scale and measure the tension in the Slinky® by hooking the spring scale on the end of the Slinky® . Record this value in Table 2

7. Now increase the tension by grabbing 20 coils and pulling them towards you.

8. Repeat Steps 4 and 6. Record these time values in Table 3. Be sure to hook all of the coils at the end of the slinky with the spring scale.

Table 1: Slinky® Measurements
Slinky Mass (kg)	Number of Loops	Mass/Loop (kg/loop)	Length (m)

Table 2: Wave Time Measurements for Relaxed Slinky®
Trial	Time (s)	Tension Force (N)

Table 3: Wave Time Measurements for Increases Tension Slinky®
Trial	Time (s)	Tension Force (N)

Post-Lab Questions

1. Did the waves seem to go any faster or slower when you tested a variety of amplitudes and frequency? Explain.

2. What did you notice about the speed of the longitudinal waves compared to the transverse waves? Why do you think this is?

3. Use data from Table 1 and Table 2 to calculate the average time it took for the wave to travel down and back. Use this time to calculate the average speed for the traveling wave on the Slinky® for both situations. Fill in Table 4 with your answers.

4. Calculate the wave speed using the formula for transverse waves. Fill in Table 4 with your answers.

5. Calculate a percent difference between your velocities and record them in Table 4.

Table 4: Slinky® Measurements
Trial	Velocity from Stopwatch (m/s)	Velocity from Tension and Mass density (m/s)	Percent Difference (%)

6. Identify two sources of error. Which method for measuring velocity do you think is more accurate? Which method do you think is more precise?