Yes, but the change you are talking about is irrelevant. It would not change the SUV's velocity by much.

Hm... I got 21.22m/s... then again, I haven't done physics in a long time and may have mis-remembered something along the way... (that was for the first one btw)

Infarction: we know the momenta of the cars sum to zero because the combined mass has no velocity. So 32 * 1100 = v * 2500. Then 35200 / 2500 = v, i.e. 352 / 25, which is 14 + 2/25 i.e. 14.08.

You use conservation of energy.. the fact that the cars will stick after the collision. Therefore you know that the collision is perfectly inelastic, so the maximum kinetic energy was lost. So, m1*V1 + m2*V2 = (m1+m2)*V

You solve the equation 1100kg * 32 m/s + 2500kg * X = [(1100+2500)*0]kg m/s

therefore x=-14.08 m/s.. which means the SUV had a velocity of 14.08 m/s in the opposite direction of car 1.

Or that way works too..

Your explanation does not use the principle of conservation of energy.

But isn't kinetic energy 1/2 mv^2?

Maybe this is why I did so bad in physics years ago...

No, you're right Infarction.

Um.. actually it does. I was referring to the law of conservation of energy.. Kinetic energy is not conserved in inelastic collisions, therefore you know that the maximum kinetic energy is lost. However, The law of conservation of energy is true for the system. The energy is transferred from kinetic energy to different kinds of energy (sound, heat, etc.)

This problem does not require you to find the kinetic energy of anything. You are simply looking for the velocity. Since it is an inelastic collision, all the kinetic energy is lost. So if you found the initial kinetic energy and the final kinetic energy (1/2mv^2), you would find the total change in kinetic energy to be (-initial kinetic energy) b/c the final kinetic energy is 0...