A woman with mass of 55 kg stands at the rim of a horizontal table having a mome

Question

A woman with mass of 55 kg stands at the rim of a horizontal table having a moment of inertia of 410 kg m2 and a radius of 1.6 m. The turntable is initially at rest and is free to rotate about a frictionless, vertical axis through its center. The woman then starts walking around the rim clockwise (as viewed from above the system) at a constant speed of1.1 m/s relative to the Earth. (1st question) With what angular speed does the turntable rotate? Answer in units of rad/s (2nd question) How much work does the woman do ON THE TABLE to set it into motion? Answer in units of J

Explanation / Answer

Momentum is conserved. Momentum before = Momentum after Everthing is at rest in the before case. So when she is walking, the table's momentum must be equal and opposite her clockwise momentum. The angular momentum formula is L = I*w The formula for moment of inertia that applies to the woman at the rim is Iw = M*R^2 You need to convert her walking speed to angular velocity, w, in radians/s. The formula is w = speed/r I said the table's momentum must be equal and opposite her clockwise momentum. So Ltable + Lwoman = 0 Itable*wtable + Iwoman*wwoman Forgot the work part. The woman's work on the table became the kinetic energy of the table. Angular kinetic energy is given by KEa = (1/2)*I*w^2

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