The net force of the object is equal to the force applied minus the force of friction. 
                         Fnet = ma = F - Ff
                           12 kg x 0.2 m/s² = 15 N - Ff
The value of Ff is 12.6 N. This force is equal to the product of the normal force which is equal to the weight in horizontal surface and the coefficient of friction.
                             Ff = 12.6 N = k(12 kg)(9.81 m/s²)
The value of k is equal to 0.107. 
        
             
        
        
        
Dissolves limestone and other rocks.
        
                    
             
        
        
        
Answer:
to have an accurate measure
Explanation:
 
        
             
        
        
        
It's Photoelectric Effect, I just a test with this same question. I am not good for explaining exactly how, but I was right.