String Wave Spinner

Key Features:

• 12 ft neon-colored nylon string
• L-shaped spinner attachment
• Compatible with standard drills
• Produces continuous transverse waves
• Designed for clear standing wave formation

Griff's Teaching Tips

1. Use the String Wave demonstration as a “hook” to introduce wave concepts.
   • Ask a student volunteer to hold the handle with the string wound around it. As you hold the other end with the string attachment that is secured to the drill.
   • As you and the student stand in front of the class with the string stretched out between you, open with this: “All waves - whether light, sound, or water waves - carry energy from one spot to another. The energy usually originates from something moving in a back-and-forth motion. What’s another name for that back-and-forth motion? Hint: It starts with the letter “v.” (Answer: vibration)
   • To illustrate this, briefly press the drill’s trigger button so it spins around one time and sends a wave down the string. (Note: one complete spin revolution of a rotating object typically corresponds to one cycle of vibration in the same axis.)
   • Ask students what happens to the wave as it hits the handle held by the student volunteer. (Answer: It bounces or reflects backward, also known as an echo.)
2. Next, ask students to watch what happens when you press and release the trigger several times to send multiple ways down the string. Point out for students how the waves overlap and interfere with each other.
• Now, ask students to predict what will happen if you keep your finger on the trigger to create multiple, successive vibrations. (Predictions will vary. Many students often say the wave motion on the string will be chaotic.)
• If the drill is a 2-speed drill, set the speed to low. First, press and hold the trigger about halfway down (to get a half speed at the low-speed setting).
• Guide the students through their observations with the following prompts:
• Check out the shape of the wave. What do you notice?
• Can you see the wide areas and narrow spots along the wave?
• The wide areas are where the crest of the waves overlap. Also known as the antinode in a standing wave.
• The narrow spots are where the wave troughs overlap. Also known as the nodes in a standing wave.

Predict what will happen to these areas if I speed up the drill?

• If the drill is a 2-speed drill, set the speed to high.
• Press and hold the trigger all the way down to get full speed at the high-speed setting.
• Have fun varying the speed of the drill to produce standing waves of different wavelengths.

What did you notice?

• The faster the drill spun, a greater number of wide areas (crests) and narrow spots (troughs) appeared along the string.
• Inform students that the distance between the two successive crests is the wave’s wavelength. See Figures 1 and 2 below.
• Show students that the slower the drill is spun the fewer crests and troughs appear.

What’s going on?

• As the drill spins faster, it vibrates the string faster creating more waves that travel along the string. This shortens the wavelength of each wave. Here is the important thing to remember:
• The higher the wave frequency the shorter the wavelength of each wave.
• This is true for all types of waves (whether it’s string waves, water waves, sound waves, or any of the electromagnetic waves)
• (Note: If students want to learn more about the special type of wave pattern created by the String Wave Demo then do a web search for “Standing Waves”. Here is a good site: https://www.acs.psu.edu/drussell/demos/standingwaves/standingwaves.html

3. Real World Connections to Automotive Sensors:
• Inform students that understanding the relationship between a wave’s frequency and wavelength is important to engineers as they design sensors that emit and receive waves to gather key data about a vehicle’s movement and its surroundings.
• Ask students if they have noticed the small, round (about the size of a nickel or quarter) sensors in the rear bumper of most cars. Inform students that most new cars use SONAR or sound wave sensors in their bumpers to detect nearby objects when parking or backing up. Just as some animals, like bats, whales and dolphins, use sound waves for echolocation, most new vehicles emit sound waves from the sensors in their bumpers to detect nearby objects.
• Then ask students if they have been in a car that detects when another car is in its blind spot or when another car or object is too close to the front of the car? Explain how a different type of crash avoidance sensor (fundamentally different from the sound wave sensor) utilizes electromagnetic wave technologies like radar, visible-light cameras, and lidar, to identify imminent collisions, erratic driving behavior, or obstacles in the vehicle's path thereby contributing significantly to reducing the severity and frequency of collisions, ultimately saving lives on the road.

Frequently Asked Questions

What does the String Wave Spinner demonstrate?

It demonstrates transverse waves, standing waves, and the relationship between frequency and wavelength in a visible, hands-on way. 

How does changing the drill speed affect the wave?

Increasing the drill speed increases frequency and decreases wavelength, allowing students to observe the inverse relationship between the two. 

What equipment is required to use this product?

A standard drill is required to drive the spinner. The drill is not included. 

How long is the string?

The kit includes 12 feet of neon-colored nylon string for clear visibility during demonstrations.

What grade levels is this best for?

It works well in middle school physical science, high school physics (CP, Honors, AP® Physics 1), and introductory college physics courses.