Eh not really sure bout this one
Answer:
D) equal to the flux of electric field through the Gaussian surface B.
Explanation:
Flux through S(A) = Flux through S (B ) = Charge inside/ ∈₀
Answer:
v = 7.67 m/s for L= 1m
Explanation:
Let's use the conservation of mechanical energy, at the highest point and the lowest point
Initial. Vertical ruler
Em₀ = mg h
Final. Just before touching the floor
= K = ½ I w²
Em₀ = 
m g h = ½ I w²
The moment of inertia of a ruler that turns on one end is
I = 1/3 m L²
Let's replace
m g h = ½ (1/3 m L²) w²2
g h = 1/6 L² w²
They ask for the speed of the end so the height h is equal to the length of the ruler
g L = 1/6 L² w²
The linear and angular variables are related
v = w r
w = v / r
In this case the point of interest a in strangers r = L
g L = 1/6 L² v² / L²
v = √ 6 g L
Let's calculate
Assume that the length of the meter is L = 1 m
v = √ (6 9.8 1)
v = 7.67 m/s
Answer: 3.12 * 10^12 F ( 3.12 pF)
Explanation: To calculate this capacitor of two hollow, coaxial, iron cylinders, we have to determine the potental differente between them and afeter that to use C=Q/ΔV
The electric field in th eregion rinner<r<router
By using the Gaussian law
∫E*ds=Q inside/εo
E*2*π*rinner^2*L= Q /εo
E=Q/(2*π*εo*r^2)
[Vab]=\int\limits^a_b {E} \, dr
where a and b are the inner and outer radii.
Then we have:
ΔV= 2*k*(Q/L)* ln (b/a)
replacing the values and using that C=Q/ΔV
we have:
C= L/(2*k*ln(b/a)=0.17/(2*9*10^9*3.023)=3.12 pF