- #1
ph123
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A woman with a mass of 45.0 kg is standing on the rim of a large disk that is rotating at an angular velocity of 0.490 rev/s about an axis through its center. The disk has a mass of 120 kg and a radius of 4.50 m. Calculate the magnitude of the total angular momentum of the woman-plus-disk system. (Assume that you can treat the woman as a point.)
Ok, well I first converted rev/s into rad/s.
0.490 rev/s * 2(pi) = 3.079 rad/s
Next I determined that the moment of inertia for a disk is
(1/2)mr^2
Next I used the equation for angular momentum:
L = I(omega)
= [(1/2)mr^2]omega
= [(1/2)(120 kg + 45 kg)(4.50m)^2]*3.079 rad/s
= 5143.8 kg m^2/s
This one seemed really straightforward to me, but the program I use for physics says the answer isn't right. Anyone know what I did wrong?
Ok, well I first converted rev/s into rad/s.
0.490 rev/s * 2(pi) = 3.079 rad/s
Next I determined that the moment of inertia for a disk is
(1/2)mr^2
Next I used the equation for angular momentum:
L = I(omega)
= [(1/2)mr^2]omega
= [(1/2)(120 kg + 45 kg)(4.50m)^2]*3.079 rad/s
= 5143.8 kg m^2/s
This one seemed really straightforward to me, but the program I use for physics says the answer isn't right. Anyone know what I did wrong?