The longer you spend reading and thinking about this question, 
the more defective it appears.
-- In each case, the amount of work done is determined by the strength 
of
the force AND by  the distance the skateboard rolls <em><u>while you're still
</u></em>
<em><u>applying the force</u>.   </em>Without some more or different information, the total 
distance the skateboard rolls may or may not tell how much work was done
to it.<em>
</em>
-- We know that the forces are equal, but we don't know anything about 
how far each one rolled <em>while the force continued</em>.  All we know is that 
one force must have been removed.
-- If one skateboard moves a few feet and comes to a stop, then you 
must have stopped pushing it at some time before it stopped, otherwise 
it would have kept going.  
-- How far did that one roll while you were still pushing it ?
-- Did you also stop pushing the other skateboard at some point, or 
did you stick with that one?
-- Did each skateboard both roll the same distance while you continued pushing it ?
I don't think we know enough about the experimental set-up and methods 
to decide which skateboard had more work done to it.
        
                    
             
        
        
        
B. F<em>spring = k(triangle)</em> x
 
        
             
        
        
        
Given :
A spring with a spring constant of 1730 N/m is compressed 0.136 m from its equilibrium position with an object having a mass of 1.72 kg. 
To Find :
The embankment in the height.
Solution :
Since no external force is acting in the system, therefore total energy will be conserved.
Initial kinetic energy of the object = Energy stored in spring

Also, initial potential energy is 0.
Now,

Therefore, the embankment height is 0.64 m.