What is the motion of ocean waves?
The students will be able to explain and to demonstrate the movement of ocean waves.
Small rectangular pan, Cork stopper
Optional Objects: Pencil; Water, SpoonLeaf; Piece of sponge; etc.
If you place a cork bobber on the surface, it bobs up and down as a wave passes (unless caught in a current!). If you watch carefully you would see that the cork is lifted up by the first slope of the wave. It is carried forward to the top, or crest, of the wave, and then slides down the rear slope. In actuality the cork may have only moved an inch or two.
When a wave comes near the shore, the motion changes. The bottom of the wave touches bottom, slowing it down. The crest is not slowed down, but continues to move at nearly the same rate, and finally, spills over. After a wave spills over, smaller waves may be formed. The same processes take place in the smaller waves.
Do the following experiment to show how waves travel over water.
1. Fill the pan with water.
2. Place the cork carefully on the top of the water. Wait until the cork stops moving.
3. Gently but steadily hit the top of the water at one end of the pan with the spoon until waves are made.
4. Make observations and fill in the Experiment Form.
Some questions to use in a class discussion are —What happened to the cork? Did the cork move across the water with the wave? What does this seem to show about the movement of water in a wave? What happened to the different objects?
Additional Activity: Ocean waves always wash against the shore. In what ways do you think waves can change the shape of the shoreline over the years? Write at least two ways in your paper.