AP Ferryman Lab

Most lab reports were pretty good. However many of you persist in the use of triangles in inappropriate ways. Try to outgrow triangles and think in terms of vectors and components. When drawing vector additions or triangles some of you seem to be incapable of placing the base at the top. In the ferryman Part 2 it seems natural to place the 30. m length at the top since it is the displacement along the north shore, but many of you drew it at the bottom and thus had the boat either going northwest or southeast graphically when it was of course going northeast.

Part 3: Some of you are still ignoring the process of finding relative velocity. You just assume that the 20 m/s vboat,water is a leg and the river current is another leg and you get a wrong right triangle. You need to use the idea that vboat, shore = vboat,water + vwater,shore and recognize that vboat,shore( the sum or resultant) must have zero x component. This leads to vboat,water's x component must = -vwater,shore ( also known as the current). In this case the addition of a diagonal vector ( one with north and east components) and an - east only vector ( the current) is a North only vector.