can test the velocity-addition ideas in the first section of this chapter. A small battery-powered or wind-up boat is also necessary. These can be found in toy or variety stores.
a. Test your boat first in the bathtub or a pond to estimate how fast it can move in still water.
b. Find a place in the stream where the current is slow and smooth (no eddies). Drop a twig in the stream, and with the help of a watch, estimate the velocity of the current.
c. Place your boat, with its motor running, in the stream with the boat pointed downstream. Estimate its velocity relative to the bank. Does the result agree with what you would predict based on the addition of relative velocities?
d. Will the boat move upstream? (If the current is too strong, it may be difficult to keep it headed in this direction.)
e. Try pointing the boat across stream in a location where the current is as uniform as possible. What do you have to do to get the boat to cross the stream?