Question

Assume that all of the mass of a bicycle wheel is concentrated at its rim. Such a wheel of mass 1.2 kg and radius 30 cm starts from rest at the top of a hill 100m long and inclined at 20 degrees to the horizontal. What will be the speed of the wheel at the bottom of the hill if it rolls without slipping?
The answer is 15 m/s.

I keep getting 18.3 m/s. Could someone please help. Thank you!

Answer 1

gain in energy = m g h = 1.2 * 9.81 * 34.2
= 403 Joules

403 = (1/2) m v^2 + (1/2)I omega^2

I = m r^2 = 1.2 (.09) = .108
omega = v/r = v/0.3
so
403 = (1/2)(1.2)(v^2) +(1/2)(.108)(v^2)/.09

403 = v^2 ( .6 + .583)
v = 18.5 m/s
I agree with you

Answer 2

lit. crazy. movie.