1. The problem statement, all variables and given/known data

Blocks A and B are moving toward each other. Block A has a mass of 2.0 kg and a velocity of 50 m/s, while B has a mass of 4.0 kg and a velocity of -25 m/s. They suffer a completely inelastic collision. The kinetic energy dissipated during the collision is:

2. Relevant equations

3. The attempt at a solution
So my professor has already worked out this problem, but I’m having trouble understanding why she picked the equations she did and how she manipulated them.

m1v1i-m2v2i=(m1+m2)V

Plug in the numbers and you get V=0

ΔK=$\frac{1}{2}$(m1+m2)V2-($\frac{1}{2}$m1v1i2+$\frac{1}{2}$m2v2i2)

Plug in and get -3750J

http://ift.tt/PmdIMl