Question

A student holds two lead weights, each ofmass
9.6 kg. When the students’ arms are extended
horizontally, the lead weights are 0.92 m from
the axis of rotation and the student rotates
with an angular speed of 1.8 rad/sec. The
moment of inertia of student plus stool is
5 kgm2 and is assumed to be constant; i.e.,
the student’s arms are massless! Then the
student pulls the lead weights horizontally to
a radius 0.23 m from the axis of rotation.

Calculate the final angular speed of the
system.
Answer in units of rad/s

Answer 1

Think what quantity is conserved in the process.

Answer 2

is inertia conserved?

Answer 3

Inertia is not a quantity.

Mass, momentum, kinetic energy, moment of inertia, angular momentum... are quantities.