An experiment was performed on a 2-kg block. forces of 5, 10 and 15 newtons respectively were applied to the block for 5 seconds. describe the difference in final speed between the three trials.

From Newton's second law of motion, 
                                     F = ma = mv/t
Where F is force, m is mass, a is acceleration, v is velocity, and t is time. Substituting the known values from the given,
   (a)          5 N = (2 kg)(v)/(5 s)    ;     v = 12.5 m/s
    (b)        10 N = (2 kg)(v) /(5 s)  ;     v = 25 m/s
   (c)          15 N = (2 kg)(v) /(5s)  ;      v = 37.5 m/s

Therefore, the greater the amount of force, the higher is the final velocity of the block. 

A. they hold atoms  together with a molecule.its a force that exist between molecules. hope this .