Answer:
Fd
Explanation:
Work is force times distance. If you push on an object really hard but it does not budge, you have still performed no work on it, because anything times zero is still zero. 
 
        
                    
             
        
        
        
Answer: was it this problem?
Explanation:
 
        
             
        
        
        
heat from water goes into air in ball
air expands
ping goes the dent
 
        
                    
             
        
        
        
Answer:
it is essential that the charge on the plates are of the same magnitude, but in the opposite direction
Explanation:
The configuration of parallel plates is called a capacitor and is widely used to create constant electric fields inside.
  To obtain this field it is essential that the charge on the plates are of the same magnitude, but in the opposite direction
This is so that the fields created by each plate can be added inside and subtracted from the outside of the plates