AP PHYSICS
posted by paul .
the height of the upper falls at Yellowstone falls is 33.2m. when the water reaches the botton of the falls, its speed is 25.8 m/s. neglecting air resistance, what is the speed of the water at the to of te falls.

The water acquires a vertical velocity component during the fall equal to
Vy = sqrt(2gH) = 25.5 m/s. Its velocity at the bottom is 25.8 m/s, so the horizontal component at the bottom must be sqrt[(25.8)^2  (25.5)^2] = 3.9 m/s
That must be the horizontal component at the top also, since it does not change during the fall. It is the velocity magnitude there.