Answer:
a) R = ρ₀ L /π(r_b² - R_a²)
, b) ρ₀ = V / I π (r_b² - R_a²) / L
Explanation:
a) The resistance of a material is given by
R = ρ l / A
where ρ is the resistivity, l is the length and A is the area
the length is l = L and the resistivity is ρ = ρ₀
the area is the area of the cylindrical shell
A = π r_b² - π r_a²
A = π (r_b² - r_a²)
we substitute
R = ρ₀ L /π(r_b² - R_a²)
b) The potential difference is related to current and resistance by ohm's law
V = i R
we subsist the expression of resistance
V = I ρ₀ L /π (r_b² - R_a²)
ρ₀ = V / I π (r_b² - R_a²) / L
First we gotta use an equation of motion:

Our vertical distance d= 100 m, initial vertical speed u = 0 m/s (because velocity is fully horizontal), and vertical acceleration a = 9.8 m/s2 because of gravity. Let's plug it all in!

Now we just need to solve for t:

Hit the calculators, and you'll get 4.5 seconds!
Answer:
5.791244495 KNm
Explanation:
The height h is given by,
Potential energy, PE is given by
PE=mgh where m is mass of the woman, g is acceleration due to gravity whose value is taken as
and h is already given hence substituting 77 Kg for m we obtain
PE=21.6567095 KNm
We also know that Kinetic energy is given by
where v is the velocity and substituting v for 20.3 we obtain
KE=15.865465 KNm
Friction work is the difference between PE and KE hence
Friction work=21.6567095 KNm-15865.465 Nm=5.791244495 KNm
Impulse = Ft=mΔv => Δv = Ft/m = 4.28/0.18 = 23.78 m/s
But,
Δv = v1-v2, where v1 = initial velocity = 16 m/s, v2 = final velocity
Therefore,
v1 - v2 = 23.78 => v2 = v1 - 23.78 => v2 = 16 - 23.78 = -7.78 m/s
The velocity of ball after the force is 7.78 m/s in the direction of the force.