Centre of Mass then axis of rotation and then moment of inertia. This was the toughest question for your level... happy to help ^_^. It was purely experimental question.
Answer:
Resistance of gold wire, 
Explanation:
In this question we have given
Density of gold, 
resistivity of gold, 
Length of wire, 
Temperature, 
We know that relation between volume and density is given as

Therefore, volume occupied by one gram gold is given as,
.........(1)
We Know that Volume of gold wire which is cylindrical in shape is given by following formula
......(2)
Here,
...........(3)
here A is the cross sectional area of cylendrical gold wire
From equation 2 and 3
we got
...............(4)
on comparing equation 1 and equation 4, we got,



we know that resistance and resistivity are related by following formula,
................(5)
Put values of resistivity, A and L in equation 5, we got


Therefore resistance of gold wire, 
Since they do not stick after collision hence collision is elastic. In elastic collision, both momentum and kinetic energy is conserved because in this type of collision, first body deforms but then quickly regains its former shape and transfers its kinetic energy to the second pluck.
So kinetic energy is conserved.
<span>The condition alone that is necessary so that the final kinetic energy of the system is zero after the collision is that the
objects must have momenta with the same magnitude but opposite directions.</span>