A. The cliff was 30.7 m high
B. I also got 9.5 as the horizontal distance 
Here is my work, I find making charts like this one to find knowns and unknowns can be helpful
 
        
        
        
4A. PE = MxGxH. (You can consider g as 9.8 / 10m/s as well)
 509 J = 12x10xH
 
 509 J = 120xH
 
 H = 509/120 
 
 H = 4.24 m
Hope u got the answer....pls rate the answer if it is helpful for u....and I'm sorry I could not understand B part so I didn't do it.
Thank you
 
        
             
        
        
        
Answer:the rate changes during the position of the object
Explanation:so there is no object that has the same rate but unless it is a specific one like a care but it changes during the position of the object 
 
        
             
        
        
        
E) Protons, neutrons, and electrons