How to measure the speed of sound with two lumps of wood ...

Picture of How to measure the speed of sound with two lumps of wood ...
... a stop watch and a convenient wall.
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Step 1: The idea

Speed is how far something travels in a known time speed = distance / time.

In everyday life, speed is generally measured in either miles per hour (or kilometres per hour; most of the world is metric). Higher speeds, especially in a scientific or engineering context, are usually measured in metres per second (m/s, ms-1), and that is what we will use in this Instructable.

We will measure the time it takes for sound to travel a known distance by using rhythmic echoes.

Step 2: The equipment

To time echoes accurately, we need a short pulse of loud sound. Two solid lumps of wood are ideal.

To generate an echo, we need a hard flat surface in a fairly uncluttered space. A wall in a school playground is perfect.

We need to time the echo's journey, so we need a stopwatch. Actually, we are going to use several stopwatches to eliminate human error: a small group of Science Clubbers will each use a stopwatch, and an average will be taken of their results,

To find the distance? part of the equation, we need to know how far we are from the wall. This should be measured in metres, either with the school-child's favourite, the click wheel, or with a dirty great tape measure.
oaxacamatt3 years ago
Great experiment! Just up the right thing for 10 yr olds I would think too. Bang stuff, listen for the noises then time it. what could be more fun.
rimar20003 years ago
Very interesting!
Murdok8 years ago
I tried this and got a hernia...do you have to use lumber? *Couldn't resist; saw someone else up there make "wood" joke.
heh... wood
Kiteman (author) 8 years ago
Hey, Eric, happy now?
When I saw this I just thought, "Man, where's that guy with the professor avatar. He was talking about this just a couple days ago."
Kiteman (author)  JakeTobak8 years ago
How long do you think you can get away with having a comment like this and no Instructable showing us how?


You ask, I give.
You'll notice me proudly in the "They Like It" box. I like the rhythm aspect of the project to deal with short time durations.
Kiteman (author)  ewilhelm8 years ago
>smug grin<
trebuchet038 years ago
I remember doing this in high school :) Nice work :)
lemonie8 years ago
Yea, we did this at school! Think it was two planks, and we had a good, big, brick, Comprehensive wall. L