Force on the car in a collision

[haruspex]

how do we define a force again, I think my error lies there , is it not the change of momentum rather than the momentum

It's neither.
A force is something one body exerts on another. A consequence of a force acting over a period of time can be a change in momentum.

I am thinking really on a resultant

Sure, but you have to identify the body acted on. If you fix on one of the cars, the other car exerts a force on it during the impact, but it does not exert a force on itself, so the resultant is not zero.
To get a zero resultant here you need to introduce a third object for both cars to act on.

 

[Nile Anderson]

It's neither.
A force is something one body exerts on another. A consequence of a force acting over a period of time can be a change in momentum.

Sure, but you have to identify the body acted on. If you fix on one of the cars, the other car exerts a force on it during the impact, but it does not exert a force on itself, so the resultant is not zero.
To get a zero resultant here you need to introduce a third object for both cars to act on.

Newton's Second Law ?

 

[haruspex]

Newton's Second Law ?

Applied here how, exactly?

 

[Nile Anderson]

F=mv-mu/t=m(v-u)/t=ma

 

[haruspex]

F=mv-mu/t=m(v-u)/t=ma

I asked exactly how you are applying it in the present context. Which body has mass m? What force acting on the body is represented by F? What time period does t stand for?
Anyway, F=m(v-u)/t is not quite right. That will give you the average force over the time interval t. Likewise, your a is the average acceleration.,

 

[Nile Anderson]

I see , interpretation then

 

[haruspex]

I see , interpretation then

No, not interpretation, application. It doesn't mean anything to quote a law in relation to a problem if you cannot state how the entities in the law relate to those in the problem.

 

[Nile Anderson]

No, not interpretation, application. It doesn't mean anything to quote a law in relation to a problem if you cannot state how the entities in the law relate to those in the problem.

I say interpretation to say that you are completely right my friend , I have thought about it and that is what I meant you are right , I started with in inaccurate point, trying to defend that point , but deduction can truly get you know where with an incorrect base

 

[haruspex]

I say interpretation to say that you are completely right my friend , I have thought about it and that is what I meant you are right , I started with in inaccurate point, trying to defend that point , but deduction can truly get you know where with an incorrect base

OK.