Calculating Impulse and Energy in a Car Collision

[MooPhysics]

Homework Statement

A car initially at rest accelerates North for 10seconds. At 11seconds a second car heading west at (Time given in Km/h) collides with the first car at a cross intersection. The cars stick together and slide off across the intersection at (Vf given in KM/h). How much energy was transformed into heat? What is the Impulse of the first cars engine?
Mass of Car1 (Given in kg) (m1)
Mass of Car2 (Given in kg) (m2)
Velocity of Car 2 (v2)

Homework Equations

m1v1=(m1+m2)v2
I=p (Change in momentum p)
p= m*v (Change in Velocity)
F*t=m*v3. Attempt
My question is: How do I figure out the velocity of the first car? I have tried v1=(m1+m2)v2/m1 but I am unsure if I am on the right track due to the car1 accelerating. Would the initial velocity for Car1 be vi=0 due to the car starting off at rest? I can't seem to work out the acceleration due to not having the distance given to me. Is there a formula I may have not considered here? I have a feeling I need to work backwards, but not sure where to start.

When the question asks about energy to heat, is it talking about Kinetic Energy. I thought some of the energy would have been absorbed do to the collision?

 

[kuruman]

Can you post the problem exactly as it was given to you? Were you given any numbers? If so, what are they? Time is not usually given in km/h.
Your attempt at a solution assumes motion in one dimension. This is not the case here. You need to conserve momentum in two dimensions and write down some vector equations.

 

[MooPhysics]

The question is:

Initaially at rest, a car (mass= 1240kg) accelerates north from a set of traffic lights at a constant rate for 10s. 11 seconds after starting to accelerate it crosses an intersection and is hit by a second car (mass=1124kg) heading west at 65km/h. The two cars stick together and slide off from across the intersection at 32km/h. How much energy was transformed into heat, damage or sound in the collision and how much impulse did the engine of the first car provide while it was accelerating?

 

[haruspex]

unsure if I am on the right track due to the car1 accelerating.

When the collision occurs, what parameters determine the outcome? Can it matter what the history is leading to those parameters?

You quoted a momentum conservation equation for coalescence, but remember momentum is a vector. So that is really two equations. You know the final speed, so how many unknowns do you have in those two equations?

 

[MooPhysics]

Oh I see where I went wrong! Thank you for your help. I don't know why, but I didn't even consider it to be a 2 dimension. I think I have all the information I need to answer this now.