F = mass * acceleration which is all about momentum. The momentum of a semi is 10x the momentum of an SUV.
When you have a 56,000lb loaded semi travleing at 60 mph it is going to obliterate a 5,000 pound SUV going in the opposite direction. The energy differential between the two is so large the SUV vector energy barely registers against the semi vector energy. A bomb is an applicable analogy in the amount of energy dispersed when the SUV gets rammed. Even if you are going in the same direction at similar speeds any contact with vehicles of a much larger mass isn't going to be good. If you cut in front of a semi to make an exit make sure there is room so you aren't going to get bumped from behind because you will be launched.
This is why you see trucks "charging" hills because they require 11 times the energy to make it up the same hill as a psuedo truck does. They try to conserve momentum from the backside of the previous hill so they can carry it up the first 1/2 of the next uphill.