Experiment in Sound
Try this experiment in sound, and find out if sound travels better through some materials than others.
What You'll Need:
- A partner
If you've ever watched old westerns, you may have seen a character put one ear to the ground and announce that the cavalry was coming, or listen to the rail of a train track and know that a train was on its way. Does this really work?
To find out, go to a playground with a partner on a warm day.
Step 1: Have your partner go to the other side of the playground, then run back. Raise your hand as soon as you can hear the sound of your partner's running feet.
Step 2: Have your partner run across the playground again, but this time put your ear to the ground. See if you can hear your partner's feet sooner.
Here's another variation on the experiment:
Step 1: When it's not too hot or too cold, find a long, metal object such as a chain-link fence post (watch out for loose metal). Stand at one end and have your partner tap the post.
Step 2: Put your ear to the rail and have your partner tap again. Does it sound different? Does it seem louder?
You can also try the same experiment with the materials around you. Does sound travel better through some materials than others? Do some materials muffle sound?
Sound waves are waves of energy that move the molecules of the substance they travel through. Air molecules are much farther apart than the molecules of solid metal.
Consider the density of the material (that is, how close together the molecules are) as you try to figure out why sound would move through metal better than through air.
Keep reading to learn how to make a device that lets you follow the clouds and see where the wind's blowing.
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