Materials: Bathtub, watch or timer, and ruler.

1. Fill a bathtub with water to a depth of 20 cm, then gently sweep the water (just below the surface) with your forearm over the entire width of the tub. After lifting your arm you will see a traveling wave (sloshing wave) moving across the tub. Be sure to verify that you have created a shallow wave. Measure the speed (in m/s) of the wave by timing a wave crest for as many tub lengths as possible. Speed = Distance moved/time . Repeat several times.

2. Measure the speed of the tidal wave for depths up to 40 cm, at 4 cm intervals, as in 1. Construct a table of speed v(in m/s) Vs depth h(in m). What trend do you observe?

3. Plot a graph v (vertical axis)Vs h(horizontal axis), and a graph of v Vs h^(0.5) . Which of the two is closer to a straight line? Trace a line going through the points that best fit the data. From a given point on the line draw a vertical line down of height H then a horizontal line to the left of length B till it meets the line again. The slope of the line = H/B .

4. The speed of the tidal wave will then be v = (slope)*( h or h^0.5 ) .

5. As an application, estimate the speed of a huge tidal wave called "tsunami", which is excited by undersea earthquakes. Take an average depth in the deep ocean to be h = 4000 m and use your formula. If this wave is generated near Hawaii, how long will it take to reach the coast of California?

6. Discuss sources of error and any interesting observations about the experiment.