Question

1)

A student sitting on a chair on a circular platform of negligible mass rotates freely on an air table at initial rotational speed 2.3 rad/s. The student's arms are initially extended with 6.0-kg dumbbells in each hand. As the student pulls her arms in toward her body, the dumbbells move from a distance of 0.80 m to 0.10 m from the axis of rotation. The initial rotational inertia of the student's body (not including the dumbbells) with arms extended is 6.0 kg⋅m^2 and her final rotational inertia is 5.0 kg⋅m^2.

a) Determine the student's final rotational speed. Express your answer in radians per second.

b) Determine the change of kinetic energy of the system consisting of the student together with the two dumbbells. Express your answer with the appropriate units.

c) Determine the change in the kinetic energy of the system consisting of the two dumbbells alone without the student. Express your answer with the appropriate units.

d) Determine the change of kinetic energy of the system consisting of student alone without the dumbbells.Express your answer with the appropriate units.

1) e)

A ballet student with her arms and a leg extended spins with an initial rotational speed of 1.0 rev/s. As she draws her arms and leg in toward her body, her rotational inertia becomes 0.80 kg⋅m^2 and her rotational velocity is 5.0 rev/s.

Determine her initial rotational inertia.

Express your answer with the appropriate units.

Answer 1