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## Homework Statement

A car is driving and hits the brakes for

*l*distance before colliding with another car at rest who has the brakes on. After the collision they slide distance

_{1}*l*together while braking.

_{2}The mass of both cars are known, and the friction between the road and the wheels is known as well.

Find the velocity of the car driving right before it hits the brakes.

## Homework Equations

Something with momentum and impulse perhaps?

## The Attempt at a Solution

Originally, I thought about using the total momentum equation, however I do not know any of the velocities before or after the collision. I only know the velocity of the car at rest before the collision.

[itex]m_Av_{A1x}+m_Bv_{B1x}=(m_A+m_B)v_{2x}[/itex]

Where A denotes the moving car and B denotes the car initially at rest. 1 is before the collision and 2 is after.

I want to find [itex]v_{A1x}[/itex] and I know that [itex]v_{B1x}=0[/itex] but that still leaves me with [itex]v_{2x}[/itex].

Besides I don't even think that this equation is correct because I haven't taken the friction force into consideration.

Can somebody lead me to the right direction?