Kinetic energy is the energy the makes an object move.
When you hit a ball it collides with the bat. When you catch a ball it collides with your hand.
Honestly, giving. I know that receiving may feel very good, and you get that new thing that you wanted but if you give, you feel really good when you see that smile on someone else’s face.
(a) 
The moment of inertia of a uniform-density disk is given by

where
M is the mass of the disk
R is its radius
In this problem,
M = 16 kg is the mass of the disk
R = 0.19 m is the radius
Substituting into the equation, we find

(b) 142.5 J
The rotational kinetic energy of the disk is given by

where
I is the moment of inertia
is the angular velocity
We know that the disk makes one complete rotation in T=0.2 s (so, this is the period). Therefore, its angular velocity is

And so, the rotational kinetic energy is

(c) 
The rotational angular momentum of the disk is given by

where
I is the moment of inertia
is the angular velocity
Substituting the values found in the previous parts of the problem, we find

Iron is the best conductor in this group.