Developed by W. K. Adams
Students explore the speed of sound by experiencing the delay for sound to reach them when they know a noise has been made. They will explore what it feels like to identify objects from a distance.
Speed of sound
45 minutes allows for time to get to and from the field as well as time to do the activities. If you’re escorting younger children, the activity may take up to 50 minutes.
Students will be able to:
• Describe that there is a delay between when they see a sound happen and when they hear it
Materials not in Kit
A very large field, 200 yards or bigger (twice the length of a football field)
A rock and Metal post (such as a fence post)
7 different objects
6 landscaping flags (or other markers)
*Since students will be outside and spread out, you might want to have extra supervision.
- Label the 7 different objects with numbers 1-7.
- Set up the field with landscaping flags (or other eco-friendly markers) every twenty large paces (or every 20 meters) from the metal pole until you reach 100 meters, then place the last maker at the 200-meter mark.
- Leave that rock, and 7 objects next to the metal post.
Introduce the Activity
Discuss the following question to get students thinking about the speed of sound.
→ Why do you think you can see fireworks before you hear the boom?
Explain that the class will be going outside for the remainder of the activity. You should also identify any safety concerns that may exist.
Doing the Activity
Speed of Sound
- The class will travel to the field set up with the markers. Have the students stay 200 feet away from the metal post.
- Ask the class why you think you can see fireworks before you can hear the boom.
- Have an assistant walk to the metal post that’s 200 meters away from the rest of the class (the length of two football fields).
- NOTE: It’s very important to be this far away to show the delay of sound. We tried 100 meters and the delay wasn’t large enough.
- With a large, visible arm motion, the assistant will strike the metal post with a rock. The assistant should do this at least 10 times. It’s helpful to prearrange a signal for the assistant to know when to stop hitting the post.
- Discuss the following questions with the class:
- Do you hear the sound at the same time that you see the rock hit the post?
- Why do you think this is?
- How can you tell how far away lightening is?
- Briefly demonstrate the calculation for the speed of sound. The speed of sound in air in Colorado is about 750 miles per hour. Calculate how many seconds it takes sound to travel 1 mile (time = distance/speed).
This is where the rule of thumb comes from that says for every five “one-thousands” that you count, the lightening is a mile away from you.
Identification from a Distance
- Students should go to a point that is 100 meters away from the metal post, halfway across the field. They should each create an Identification from a Distance chart (see below for an example) and a writing utensil.
- Explain that at this distance – using echolocation – a dolphin can identify small fish just 6 inches in length and some bats can identify a certain type of moth with a 1.25-inch wingspan!
- While the students are still 100 meters away, the assistant will hold of the 7 objects one at a time, in order. Students will look at each object and try to discern what each one is and write down their best guess on the chart, even if it’s just the color. After they have done this for all 7 objects from 100 meters away, students will up to the 80-meter mark and repeat the process. Then the same for 60 meters, 40 meters and 20 meters. The assistant should hold up the 7 objects in the same order each time.
- As soon as the students think they know for sure what the objects are, they will circle the word in their chart under that distance.
For example, they figure out object 1 is a fish at 40 meters, circler the word “fish” in the 40- meter column.
Key Lesson Terminology
Speed of Sound – the speed at which sound travels. This is very important for scientists who study sound. In air, sound travels 343 meters in 1 second (747 miles per hour), but in water, sound travels 1500 meters in 1 second (3350 miles per hour). compare these speeds to cars traveling on the highway at 65 miles per hour.
If there is extra time, students can switch roles in the Fish Finding Game and play from a new perspective.
Hard of hearing students will not be able to tell the difference between when they see the rock hit and when the sound reaches the class, so other students could raise hands when they hear the sound. This way the student can still tell that there is a difference between when a sound is created and when it reaches a specific location.