Answer:
(a) 
(b) 
Explanation:
(a) The surface current density of a conductor is the current flowing per unit length of the conductor.

Considering a wire, the current is uniformly distributed over the circumferenece of the wire.

The radius of the wire = a

The surface current density 
(b) The current density is inversely proportional
......(1)
k is the constant of proportionality

........(2)
substituting (1) into (2)





substitute 

Yeah yeah I just got a hold of you and I saw that you were doing a good job and I thought you were doing a good job and I thought you were doing a good job and I thought you were doing a good job and I thought you were doing a good job and I thought you were doing a good job and I thought you were doing a good job and I thought you were doing a good job and I thought you were doing a good job and I thought you were doing a good job and I thought you were doing a good job and I thought you were doing a good job.
Answer:
More force
Explanation:
Object A has more mass than object B
For object A to accelerate at the same rate as object B, it will need more force.
According to Newton's second law of motion "the net force on a body is the product of its mass and acceleration".
Net force = mass x acceleration
Now, if a body has more mass and needs to accelerate at the same rate as another one with a lower mass, the force on it must be increased.
From an energy balance, we can use this formula to solve for the angular speed of the chimney
ω^2 = 3g / h sin θ
Substituting the given values:
ω^2 = 3 (9.81) / 53.2 sin 34.1
ω^2 = 0.987 /s
The formula for radial acceleration is:
a = rω^2
So,
a = 53.2 (0.987) = 52.494 /s^2
The linear velocity is:
v^2 = ar
v^2 = 52.949 (53.2) = 2816.887
The tangential acceleration is:
a = r v^2
a = 53.2 (2816.887)
a = 149858.378 m/s^2
If the tangential acceleration is equal to g:
g = r^2 3g / sin θ
Solving for θ
θ = 67°
Since Astronaut and wrench system is isolated in the space and there is no external force on it
So here momentum of the system will remain conserved
so here we can say

initially both are at rest
so here plug in all values


so here the astronaut will move in opposite direction and its speed will be equal to 0.20 m/s