Yes, for balance.hope this helped.
        
             
        
        
        
The product of an object's mass and velocity is B.momentum.
<span>♡♡Hope I helped!!! :)♡♡
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To answer, we determine the velocity of the flea when it leaves the ground. Using the given value for distance, the velocity can be determined through the equation,
                     2a d = (Vf)² - (Vi)²
where a is the acceleration due to gravity, d is distance, Vf is the final velocity which is equal to zero and Vi is the initial velocity. Substituting the known values,
               2(9.8 m/s²)(40cm/100cm) = (Vi)²
The value of Vi from the equation is 2.8 m/s. 
The equation for determining the kinetic energy is:
                   KE = 0.5mv²
Substituting,
                  KE = 0.5(0.60 x 10^-3g)(1 kg/1000g)(2.8 m/s)²
                        KE = 2.352 x 10^-6 J