We are assuming the wheel is tangent to the ground. Unrealistic, but let's go with it.
The y coordinate is given by ...
The wheel rotates rad/sec.
When the wheel is 9 feet off the ground, then it has swept out an angle of
From , differentiating, we get
We know the angular velocity is and
Entering in the values, we get
Another way is:
Entering in the 47.71 seconds to get to 9 feet, we get:
0.157 ft/sec. as before.