Answer:
Mass has total mechanical energy, which is the sum of kinetic and potential energy. as the mass is dropping, potential energy is converted into kinetic energy so mechanical energy is preserved If there is no friction. If there is friction, some of the mechanical energy is lost as heat energy so it changes. 
Explanation:
 
        
             
        
        
        
The first one is Force & the second one Power.
        
                    
             
        
        
        
Complete Question
A 10 gauge copper wire carries a current of 20 A. Assuming one free electron per copper atom, calculate the drift velocity of the electrons. (The cross-sectional area of a 10-gauge wire is 5.261 mm2.)
mm/s
Answer:
The drift velocity is 
Explanation:
From the question we are told that 
     The current on the copper is  
      The cross-sectional area is   
 
The number of copper atom in the wire is  mathematically evaluated 
       
Where  is the density of copper with a value
 is the density of copper with a value 
            is the Avogadro's number with a value
 is the Avogadro's number with a value 
          Z  is the molar mass of copper with a value  
So 
       
 
       
 
Given the 1 atom is equivalent to 1 free electron then the number of free electron is  
          
The current through the wire is mathematically represented as 
          
substituting values 
         
=>     
        
 
 
        
             
        
        
        
Answer:
present
Explanation:
read doesn't change but write is in present tense