ScienceMakers Toolkit Manual - The History Makers

Physics
Now have the participants stand even closer together without touching. How fast do they think they can do the
vibration bump now?
Have the participants sit down. Ask the participants whether they think sound travels more quickly through
mediums that have molecules close together or far apart. Are molecules of air close together or far apart? In
what medium are the molecules closest together? (solids) Do the participants think sound travels fastest through
gases, solids, or liquids?
Find a partner, and let’s prove our theory about through which medium sound travels best.
Each pair needs a wooden board and a tuning fork. How many of you have ever used a tuning fork? Can you
show us how to use one? Please use the edge of the sole of your shoe, rather than the fl oor, to set the tuning
forks vibrating. Take turns listening to the sound produced by the fork.
Now, one person in each pair needs to place his or her ear on one corner of the wooden board. The other person
will strike the tuning fork on his or her shoe and then place the single end of the tuning fork on the corner of the
board opposite the fi rst person’s ear.
Did you hear the vibrations of the tuning fork better through the air or through the wooden board? Why?
Through the air, it takes sound about fi ve seconds to travel one mile. That’s very fast, but through water, sound
can travel one mile in just over one second. I haven’t seen fi gures on how fast sound travels through wood, but
through steel, sound can go over three miles in just one second! Are the molecules in wood closer or further
apart than in steel? So, would sound travel faster in wood or in steel?
When the molecules of a medium are vibrating and passing along sound waves, is there energy being passed
along also?
Let’s do a demo to think about this question a little more. I need you to divide yourselves into three groups
around three people. We’re going to do a demo together with you. Now, bend over so you can see the water
really well. Don’t be afraid to get up close!
Now, on the count of three, we are going to each strike our tuning forks and see if there is any energy transferred
to this water. Watch closely so you can tell us what you notice! One, two, three!
(This activity, if done with more than one person, needs to be closely coordinated to keep the fun in it. As soon
as you strike the tuning forks, place the forked ends just slightly into the water, holding them at about a
forty-fi ve degree angle to the water, with the fork facing away from you.)
Where did that energy come from?
Okay, let’s get back in our groups and do another quick activity to prove this same point. You’ll be working in
pairs again, and each pair will need a can covered with a balloon, a pinch of salt and a tuning fork - who can
tell me what a “pinch” is? Right, a very small amount! Place that pinch of salt onto the balloon. Take turns
striking the tuning fork against your shoe and holding it very close to, but not touching, the balloon. What’s
happening? What’s the best way to hold the tuning fork to make the salt crystals dance around? Take turns
with the tuning fork and see what observations you can make. Tell me one thing that you notice. (Take several
observations and play off the energy of the room.)
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