Ferris wheel has radius of 26m. At what rate is the rider's height increasing, when rider is 25 m from ground.

Answer 1

You did not tell us:

1. radians per second or rpm or something about speed.

2. jow high the axis of the wheel is.

Answer 2

However, given axis h, with 26 <= h <= 51 (why?) and angular speed ω, the height

h(t) = h + 26sin(ωt)
dh/dt = 26ω cos(ωt)

so, solve for t when h=25, and then find dh/dt.