Answer: 7750 J
Explanation:
Mechanical energy is potential energy added to kinetic energy. 
5000 + 2750 J = 7750 J
 
        
             
        
        
        
<span>Two plastic balls suspended by strings are placed close to each other. If they have the same charge then they will repel each other.</span>
        
                    
             
        
        
        
Answer:
Option B
Explanation:
Speed of a wave is denoted by:
v=fλ
where f is the frequency which is unchanged 15Hz and λ is the new wavelength which is 28m
v=fλ
