Idea 5of 5Builds onAcross or alongThe medium owns the speedThe medium sets the speed
Sound needs stuff
Why does sound travel faster in steel than in air?
Today you'll discover
- why there is no sound in a vacuum
- what passes the squeeze along
- why stiff, tightly packed stuff carries it fastest
Think firstA rail is struck. You hear it twice
A distant rail is struck. You hear it through the steel first, then the air. Why?
Decide first, then press Next. Watch the marked particle hand the squeeze on.
A row of dots, air particles in a tube, bunched in some places and spread in others, one dot drawn filled. After a prediction, the frames advance: the filled dot moves forward and back while the bunched region moves on. The last step asks what is wrong with a loud explosion in space.
See the whole ideathe big idea and the key word, in one place
The big idea
Sound is a squeeze passed particle to particle.
Compare themSteel is denser than air and yet far faster, because its particles are stiffly joined. Stiffness wins over density.
Key word
- speed of sound
- how fast a compression is passed along a medium: about 340 m/s in air at 20 °C, 1500 m/s in water, 5000 m/s in steel
About this modelThe coils shuttle along the line of travel; the pattern of squeezes moves on.
The coils shuttle along the line of travel; the pattern of squeezes moves on.
Ready to use it?
- Rank media by the speed of sound in them, and explain why a vacuum carries none.