What should be the resistivity of materials used for electromagnets,and why?

$A$ spherical insulating ball and a spherical metallic ball of the same size and mass are dropped from the same height. Choose the correct statement out of the following (Assume negligible air friction).

$A$ bar magnet is released from rest along the axis of a very long vertical copper tube. After some time,the magnet will:

Explain eddy currents using the example of a small magnet falling through an aluminium pipe.

$A$ metallic ring connected to a rod oscillates freely like a pendulum. If a magnetic field is applied in the horizontal direction such that the pendulum swings through the field,the pendulum will:

$A$ copper ring is held horizontally and a bar magnet is dropped through the ring with its length along the axis of the ring. The acceleration of the falling magnet while it is passing through the ring is