You can imitate the motion of P and S waves using a SlinkyŽ (the metal ones work best). The S wave can also be simulated using a piece of rope in place of a SlinkyŽ. These activities work best with a partner and on a flat surface such as a table or the floor.
P waves consist of a compessional (shortening) motion and a dilational (expanding) motion that both lie along a line. As you make your own P wave in this exercise, try to identify the compressions and dilations in the SlinkyŽ. Here's how you do it:
- Place the SlinkyŽ on a flat surface. Have your partner hold the opposite end of the SlinkyŽ. If you don't have a partner, you can tie the SlinkyŽ onto a hook in the wall or onto a door knob (close the door first) and try this activity in the air.
- Holding the other end of the SlinkyŽ, walk away from your parter, or from the wall or door.
- Stop walking away when the SlinkyŽ isn't sagging anymore (if in the air) or there is no more slack. Don't pull the SlinkyŽ too tight; just take up the slack.
- Push your end of the SlinkyŽ towards your partner in one, quick motion (if the SlinkyŽ is suspended in the air, quickly jerk your end of the SlinkyŽ towards the wall and then back). Don't let go of the SlinkyŽ.
You'll see waves similar to P waves moving back and forth along the SlinkyŽ like in the picture below:
When making your S wave, notice how the SlinkyŽ itself moves in a direction perpindicular to the direction that the energy is traveling in (perpindicular to the direction of wave propagation). S waves are more complex than P waves, but they should be easier to simulate in this activity:
- Place the SlinkyŽ on a flat surface, and have your partner hold the opposite end of the SlinkyŽ. If working alone, tie one end of the SlinkyŽ to a hook on the wall or a door knob (close the door first).
- Holding the other end of the SlinkyŽ, walk away from your partner, or from the wall or door.
- Stop walking when the SlinkyŽ has only some slack left. If working alone and the SlinkyŽ is suspended in the air, you want to stop walking only when the SlinkyŽ no longer sags in the air. Don't pull the SlinkyŽ tight; just take up most of the slack.
- Quickly jerk your end of the SlinkyŽ from side to side once. If the SlinkyŽ is suspended in the air, a quick jerk up and down once is sufficient. Don't let go of the SlinkyŽ.
You'll see waves similar to S waves moving along the SlinkyŽ like in the picture below:
Images Š2000-2006 Lawrence Braile, used with permission. All other content is Š2007 Michigan Technological University. Permission granted for reproduction for non-commercial uses.