A student stands motionless on a frictionless turntable while holding two identical…
PHYSICS · Single correct · AP · Physics 1: Algebra-based · Energy and Momentum of Rotating Systems · Energy and Momentum of Rotating Systems
Problem
A student stands motionless on a frictionless turntable while holding two identical m-kg balls at arm’s length, each at a distance r from the rotation axis on opposite sides of the body. The student (plus turntable, but not the balls) has a moment of inertia I0 about the axis. The student simultaneously throws the two balls tangentially so that each leaves the hands moving counterclockwise at speed v in a circle of radius r centered on the axis. Neglect any external torque and assume the balls no longer interact with the student after release. Which of the following gives the magnitude of the student’s angular speed ω immediately after the balls are released?
(a) I0mrv
(b) I0+2mr22mrv
(c) I02mrv
(d) rv