<h2>Answer: electrostatic and gravitational force
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Mechanical energy remains constant (conserved) if only <u>conservative forces</u> act on the particles.  
In this sense, the following forces are conservative:  
-Gravitational  
-Elastic
-Electrostatics  
While the Friction Force and the Magnetic Force are not conservative. 
According to this, mechanical energy is conserved in the presence of electrostatic and gravitational forces.
 
        
        
        
Answer:
f =ma = 0.015 * 55 = 0.825 N 
so yeah that's ur ans 
 
        
                    
             
        
        
        
Answer:
1088 m
Explanation:
3.00 seconds times by 340 =1020+68=1088
 
        
             
        
        
        
1. Air resistance (therefore, the air density, shape (aerodynamic or not), and surface area affected
2. The gravitational acceleration constant (g = 9.8 m/s^2 on Earth)