Answer: The distance is 723.4km
Explanation:
 The velocity of the transverse waves is 8.9km/s
The velocity of the longitudinal wave is 5.1 km/s
The transverse one reaches 68 seconds before the longitudinal.
if the distance is X, we know that:
X/(9.8km/s) = T1
X/(5.1km/s) = T2
T2 = T1 + 68s
Where T1 and T2 are the time that each wave needs to reach the sesmograph.
We replace the third equation into the second and get:
X/(9.8km/s) = T1
X/(5.1km/s) = T1 + 68s
Now, we can replace T1 from the first equation into the second one:
X/(5.1km/s) = X/(9.8km/s) + 68s
Now we can solve it for X and find the distance.
X/(5.1km/s) - X/(9.8km/s) = 68s
X(1/(5.1km/s) - 1/(9.8km/s)) = X*0.094s/km= 68s
X = 68s/0.094s/km = 723.4 km
 
        
             
        
        
        
Answer:
The force is the same
Explanation:
The force per meter exerted between two wires carrying a current is given by the formula

where
 is the vacuum permeability
 is the vacuum permeability
 is the current in the 1st wire
 is the current in the 1st wire
 is the current in the 2nd wire
 is the current in the 2nd wire
r is the separation between the wires
In this problem

Substituting, we find the force per unit length on the two wires:

However, the formula is the same for the two wires: this means that the force per meter exerted on the two wires is the same.
The same conclusion comes out  from Newton's third law of motion, which states that when an object A exerts a force on an object B, then object B exerts an equal and opposite force on object A (action-reaction). If we apply the law to this situation, we see that the force exerted by wire 1 on wire 2 is the same as the force exerted by wire 2 on wire 1 (however the direction is opposite).
 
        
             
        
        
        
Answer:
              E = k Q / [d(d+L)]
Explanation:
As the charge distribution is continuous we must use integrals to solve the problem, using the equation of the elective field
        E = k ∫ dq/ r² r^
"k" is the Coulomb constant 8.9875 10 9 N / m2 C2, "r" is the distance from the load to the calculation point, "dq" is the charge element  and "r^" is a unit ventor from the load element to the point.
Suppose the rod is along the x-axis, let's look for the charge density per unit length, which is constant
          λ = Q / L
If we derive from the length we have
         λ = dq/dx       ⇒    dq = L dx
We have the variation of the cgarge per unit length, now let's calculate the magnitude of the electric field produced by this small segment of charge
         dE = k dq / x²2
         dE = k λ dx / x²
Let us write the integral limits, the lower is the distance from the point to the nearest end of the rod "d" and the upper is this value plus the length of the rod "del" since with these limits we have all the chosen charge consider
         E = k 
We take out the constant magnitudes and perform the integral
         E = k λ (-1/x)
     
Evaluating
         E = k λ [ 1/d  - 1/ (d+L)]
Using   λ = Q/L
         E = k Q/L [ 1/d  - 1/ (d+L)]
  
let's use a bit of arithmetic to simplify the expression
      [ 1/d  - 1/ (d+L)]   = L /[d(d+L)]
The final result is
      E = k Q / [d(d+L)]