This is a circular ferris wheel, with diameter of 9 meters, and the axis mounted 12 meters off the ground. The equation is the height of the a point that starts out level with the axis, at 't' seconds after the wheel starts up.
Now here's where things start to go awry:
The period of the revolution is the time it takes for the angle inside the sine to change by 2pi .
20(t - pi/2) = 2pi
20t - 10pi = 2pi
20t = 12pi
t = 12pi/20 = 1.885 seconds
I can't help it. All I did was the math, and that was bullet-proof. It was up to whoever wrote the question to guarantee that the answer makes sense.
For one thing, I don't believe the 'pi/2' belongs inside the parentheses with the 't'. But even if we take the 'pi/2' out of the parentheses, that still only makes the period 3.183 seconds, which is still an uncomfortable number ... especially for the riders.
