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Explanation:
The "speed made good" is the product of the speed and the cosine of the angle between the direction of the speed and the direction of interest. A change in height is accomplished by speed in the vertical direction.
When a spot on the Ferris Wheel is traveling vertically, as at a side position, the angle difference is zero and the cosine is a maximum. All of the vertical speed results in a change in height.
When a spot on the Ferris Wheel is traveling horizontally, as at a top or bottom position, the angle difference from the vertical is 90°, and the cosine of the angle is 0. That is, none of the horizontal speed results in a change in height.
The vertical speed is not constant because the angle of the direction of motion with respect to the vertical is not constant.
