That means, that now when I solve for the force, I'll actually get a larger force
than if I had forgotten that negative sign, very common mistake.
Solving for the average force then, notice that I end up with a negative answer,
a -1.8 x 10 to the 6th Newtons.
A couple of things I want to point out, the force is negative, which makes sense.
Because if this car were originally moving to the right with a certain velocity but
after the collision has been hit and is now moving left,
then of course the force in that collision pushed left on that car.
It changed its velocity and is now making it move left.
So we should get a negative answer.
That's what that negative sign represents, a direction to the left.
The other thing I want to point out is our time frame was very short,
while our force was very long, and that's very typical for collision problems.
They happen over very short amounts of time, and the forces can be very large.
So don't be bothered by getting a large value for force, or
a short value for time.
>> One important piece of information that I can get from this question is that
the two cars are coupled together after the collision.
This is important because if they're coupled together or attached together,
that means that this is an inelastic collision.
If it's inelastic, then what I also know is that kinetic energy is not conserved.
However, keep in mind no matter what type of collision you're looking at, all three
of the collision types have momentum, total momentum, as being conserved.
Now let's go ahead and solve for this question.
It says calculate the speed of the two cars after the collision.
Well they're stuck together so they're going to have the same speed.
The way that I'm going to solve for
this is going to allow me to use conservation of momentum.
The sum of my initial momentum equals the sum of my final momentum.
Initially I have m1v1
initial + m2v2 initial.
Say I consider vehicle 1 to be the one that was moving at 6 meters per second
left, and vehicle 2 to be the one that's at rest.
This means that m2v2 initial equaled 0.
Because these two cars have combined together after the collision,
they are now moving as one object, one mass.