C. It is answered by observation and evidence.
Good scientific explanations are defined, measurable and controllable. They can be answered by an experiment.
 
        
             
        
        
        
Answer:
 F = ⅔ F₀
Explanation:
For this exercise we use Coulomb's law
          F = k q₁q₂ / r²
let's use the subscript "o" for the initial conditions
           F₀ = k q² / r²
now the charge changes q₁ = q₂ = 2q and the new distance is r = 3 r
        
we substitute
           F = k 4q² / 9 r²
           F = k q² r² 4/9
           F = ⅔ F₀
 
        
             
        
        
        
Answer:
The radius of the loop is  20.66 km
Explanation:
let the radius of the loop be r
mass of airplane is m
At the top, the pilot experiences two radial forces, which are
1) Gravitational force is  mg
2) Centrifugal forces mv²/r out of the center
When the pilot experiences no weight, 
then, mg = mv²/r
r = v² / g
  = 450² / 9.8
  = 20.66 x 10³3
  = 20.66 km
 
        
             
        
        
        
As the density of the unknown substance is 0.68g/0.8ml = 0.85g/ml, it is less dense than the maple syrup at 1.33g/ml and will float.
        
             
        
        
        
Answer: v = 880m/s
Explanation: The length of a string is related to the wavelength of sound passing through the string at the fundamental frequency is given as 
L = λ/2 where L = length of string and λ = wavelength. 
But L = 1m
1 = λ/2
λ = 2m. 
But the frequency at fundamental is 440Hz and
V = fλ
Hence 
v = 440 * 2
v = 880m/s