Ignore part a) of the questions, I've solved that already.

But for I don't know what to say... I'm guessing something to do with Newton's third law or something. The water barrels can't exert as much force back like the bridge supports can, or something..

and for c) I know that anti-freeze freezes at a much lower temperature, but again, I don't know how to explain how ice = more damaging than water in the physics terms that they want.



any help would be appreciated.

Well if it crashes into the bridge directly, it is going to slow down much quicker than if it hit the barrels, therefore its acceleration will be much greater, and thus the net force will be much greater.

It is not asking you to solve for it directly, but it is just asking you what would happen to the net force (go up, go down, or stay the same), and we know the acceleration is going to increase, therefore the average net force on the car will increase.


For part c,

Obviously the antifreeze will remain liquid at very cold temperatures, whereas water would turn into solid ice. The solid ice would certainly not give the dampening effect that the liquid does in the barrels upon impact, so it is important that the liquid in the barrels remain in a liquid state and not freeze.

ahh thank you very much kind sir