Find the change in kinetic energy of a 0.650 kg fish leaping to the right at 15.0 m/s that collides inelastically with a 0.950 kg fish leaping to the left at 13.5 m/s

The change in the kinetic energy refers to the work done in displacing a body, thus, the change in the kinetic energy of an object refers to the work done on the object.
The correct formula to use is:
W = Initial kinetic energy - Final kinetic energy;
Where, W = change in kinetic energy
Final kinetic energy and initial kinetic energy = 1/2 MV^2
Initial velocity = 15 m/s
Final velocity  = 13.5 m/s
Initial mass = 0.650 kg
Final mass = 0.950 kg
W = 1/2 [0.650* (15 *15)] - 1/2 [0.950 * (13.5 * 13.5)]
W = 146.25 - 173.13 = 26.88
Therefore, the change in kinetic energy is 26.88 J.
 The negative sign has to be ignored, because change in kinetic energy can not be negative.

Define
m₁ = 0.650 kg the mass of the fish leaping to the right.
u₁ = 15.0 m/s is its velocity.
m₂ = 0.950 kg, the mass of the fish leaping to the left
u₂ = 13.5 m/s is its velocity.

Let v = the mutual velocity after inelastic impact.
For conservation of momentum,
m₁u₁ + m₂(-u₂) = (m₁+m₂)v
0.65*15 - 0.95*13.5 = (0.65 + 0.95)*v
v = - 3.075/1.6
   = - 1.9219 m/s 

The change in KE of the 0.65 kg fish is
(1/2)*(0.65 kg)*(15 + 1.9219)² = 93.06 J

93.1 J

  cxrcvbnmbhjtyrtdhfxbv nbmkhturytdsfxc gfxcbmgv vv fgcbvc

The objects do not reach terminal velocity         there is not enough time from the time the object falls from when it hits the ground to achieve terminal velocity. an object must be placed higher to achieve terminal velocity in order to be in free fall.