First we have to establish that the number of protons is equivalent to the atomic number of element. Here I am assuming that you are referring to Potassium (K) - 40. Potassium, stable or unstable has 19 protons.
        
             
        
        
        
The answer is reflection.
The drawing is simple but illustrates the concept beautifully.
        
                    
             
        
        
        
Answer:
her acceleration is 1 m/sec
Explanation:
The following information is given in the question 
The initial velocity is 5 m/s
After 10 seconds, she would be moved at 15 m/s
We need to find the acceleration 
As we know that
Acceleration = Change in speed ÷ time
Acceleration = (15 - 5) ÷ (10)
= 1 m/sec
Hence, her acceleration is 1 m/sec
The same would be considered