A wheel of mass M and radius R comes off a moving truck and rolls without slippi
ID: 1494796 • Letter: A
Question
A wheel of mass M and radius R comes off a moving truck and rolls without slipping along a highway. At the bottom of a hill it is moving at 10 m/s. Its moment of inertia about its rotation axis is 0.8 MR2. The wheel rolls up the hill to a stop, a height h above the bottom of the hill. An irreversible frictional loss of energy on this path is equal to one third of the total kinetic energy that the wheel had at the bottom of the hill.
(a) Calculate h.
(b) What would be the height h for a wheel in the form of a solid homogeneous disk?
Explanation / Answer
Moment of inertia = 0.8MR2
Initial velocity = 10 m/s
(a). Initial kinetic energy = (1/2)MV2(1 + 0.8) = 90M joule.
Energy lost to friction = (1/3)(90M) = 30M joule
Potential energy gained = Mgh
Now . 90M = 30M + Mgh
Or. h = 6.12 m
(b).for solid homogenious disc
Moment of inertia = 0.5MR2
Initial energy = (1/2)MV2 (1+ 0.5) = 75M
Frictional loss of energy = 25M
Now. 75M = 25M + Mgh
Or. h = 5.10 m
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