Whenever an object is in projectile motion, that is, it has 2-dimensional motion in the x and y axis, the resultant force on the object is in the y-direction.
This is because once the object has been projected, or the ball has been kicked in this case, there is no longer a force being applied on it in the x-direction. The air resistance is also neglected so the ball's final velocity in the x-direction is equal to its initial velocity in the x-direction.
However, the force of gravity cannot be neglected and causes the ball to come downwards. Therefore, after the ball has been projected, the net force on the ball is downwards, due to gravity. 
        
             
        
        
        
<span>A free body diagram is a representation of how the forces that are acting on a point or particle interact. You place your point at the origin and then draw your forces.
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Answer:(a)9.685 mm
(b)4.184 mm
Explanation:
Given 
Wavelength of light 
Width of slit(b)=0.210
(a)Width of central maximum located 1.80m from slit


=9.685 mm
(b)Width of the first order bright fringe



 
        
             
        
        
        
It would be 78 becuase the 2 percent of 64 is many of energy lost