Answer: The Sound of Silence.
 
        
             
        
        
        
When the temperature increases, the intermolecular forces between the molecules of a liquid become weaker, and some bonds break easily. Thus as temperature increases, the surface tension of a liquid decreases.
        
             
        
        
        
The distance covered by car is equal to (assuming it is moving by uniform motion) the product between the car's speed and the time of the car ride, 4 h:

where

 is the car's speed

 is the duration of the car ride
Similarly, the distance covered by train is equal to the product between the train's speed and the duration of the train ride, 7 h:

The total distance covered is S=255 km, which is the sum of the distances covered by car and train:

which becomes

 (1)
we also know that the train speed is 5 km/h greater than the car's speed:

 (2)
If we put (2) into (1), we find

and if we solve it, we find


So, the car speed is 20 km/h and the train speed is 25 km/h.
 
        
        
        
Answer:
The new Coulomb force is q₁q₂/9πε₀r²
Explanation
The coulomb force between the two charges q₁ and q₂ at a distance r in air is given by F = q₁q₂/4πε₀r².
Now, let us assume the material of dielectric constant κ = 9 is placed between them on the side of the q₁ charge. The value of its effective charge is now q₃ = q₁/κ at a distance of d = r/2 from the q₂ charge.
Since we have air between q₂ and q₃, the coulomb force between them is 
F' = q₂q₃/4πε₀d² 
= q₂(q₁/κ)/4πε₀(r/2)² 
=  4q₂q₁/κ4πε₀r² 
= 4/κ(q₂q₁/4πε₀r²) 
= 4/9 × (q₂q₁/4πε₀r²) 
= q₁q₂/9πε₀r²
So, the new Coulomb force is q₁q₂/9πε₀r²
 
        
             
        
        
        
The answer is : D
Reasoning:
Homeostasis is the body’s balance