To solve this problem it is necessary to apply the concepts related to the magnetic dipole moment in terms of the current and the surface area, as well as the current density, as a function of the current over the area.
Part A) By definition we know that magnetic dipole moment is

Where,
I = Current
S = Area

Replacing with our values we have that,

Re-arrange to find I,

Part B) To find the Current density we need to find the cross sectional area of the Wire:

Finally the current density is simply J

PART C) Finally to make the comparison with the given values we have to cross-sectional area would be

Therefore the current density would be

Comparing the two values we can see that the 2mm wire has a higher current density.
Answer:
The resistivity of the material used to make the rod is ρ= 7.5 * 10⁻⁷ Ω.m
Explanation:
R= 0.2 Ω
L= 0.8 m
S= 1.5mm*2mm= 3 mm² = 3 * 10⁻⁶ m²
ρ = (R*S)/L
ρ= 7.5 * 10⁻⁷ Ω.m
That is because there are other forces like the friction forces that apply differently on both of them. The frictional forces applied to the sled are smaller than they are on the father, for example, so it's possible for him to pull it.
Answer:
Total momentum, p = 21.24 kg-m/s
Explanation:
Given that,
Mass of first piece, 
Mass of the second piece, 
Speed of the first piece,
(along x axis)
Speed of the second piece,
(along y axis)
To find,
The total momentum of the two pieces.
Solve,
The total momentum of two pieces is equal to the sum of momentum along x axis and along y axis.






The net momentum is given by :


p = 21.24 kg-m/s
Therefore, the total momentum of the two pieces is 21.24 kg-m/s.
Momentum = mass x velocity
Before collision
Momentum 1 = 2 kg x 20 m /s = 40 kg x m/s
Momentum 2 = 3 kg x -10m/s = -30 kg x m/s
After collision
Momentum 1 = 2 kg x -5 m/s = -10 m/s
Momentum 2 = 3 kg x V2 = 3V2
Total momentum before = total momentum after
40 + -30 = -10 + 3V2
V2 = <span>6.67 m/s
Total kinetic energy before
</span><span>= (1/2) [ 2 kg * 20 m/s * 2 + 3 kg * ( -10 m/s) *2 ]
= 550 J
</span>
<span>Total kinetic energy after
</span>= (1/2) [ 2 kg * ( - 5 m/s) * 2 + 3 kg * 6.67 m/s *2 ]
= 91.73 J
Total kinetic energy lost during collision
=<span>550 J - 91.73 J
= 458.27 J</span>