A 111 kg111 kg horizontal platform is a uniform disk of radius 1.97 m1.97 m and can rotate about the vertical axis through its center. A 68.7 kg68.7 kg person stands on the platform at a distance of 1.11 m1.11 m from the center, and a 25.3 kg25.3 kg dog sits on the platform near the person 1.41 m1.41 m from the center. Find the moment of inertia of this system, consisting of the platform and its population, with respect to the axis.

The earth's magnetic field, with a magnetic dipole moment of 8.0×1022am2, is generated by currents within the molten iron of the earth's outer core. suppose we model the core current as a 3000-km-diameter current loop made from a 1000-km-diameter “wire.” the loop diameter is measured from the centers of this very fat wire.to decide whether this is a large or a small current density, compare it to the current density of a 7.0 a current in a 2.0-mm-diameter wire.