# Momentum in 2D question

• Stevo191
In summary, a grade 12 Physics class was given a basic assignment to think outside the box of typical questions. The question was about two cars of identical mass colliding at an intersection and moving away at an angle of [East 22 degrees North]. With limited information, the student struggled to solve the problem using algebra but eventually realized that breaking the final velocity into components and relating them to the initial conditions would help. The challenge of connecting concepts and equations is a common difficulty in physics and science.

#### Stevo191

So we've just finished our unit on Momentum and Energy in our grade 12 Physics class and today we were given a basic assignment that is to help us think "out-side" the box of typical questions. This particular question has me going insane...I just can't make the connection as to what to do.

The question is:

Two cars of identical mass are approaching the same intersection, one from the south and one from the west. They reach the intersection at the same time and collide. The cars lock together and move away at an angle of [East 22 degrees North]. Which car was going faster before the collision? Explain your reasoning and include all calculations.

Normally with a question like this, I'd be fine trying to solve it with all of the given variables and such (Using the m1v1i + m2v2i = m1v1f + m2v2f equation), but since this gives almost no information, I am at a loss as to how to solve it. Using logic, I know that the car traveling to the east is the one traveling faster since the final vector is going 68 degrees east, while only going 22 degrees north. How do I answer that using algebra with so little specific information? Any sort of help to point me in the right direction would be awesome...

Last edited:
Try breaking up the final velocity into components. How can you relate them to the whole / each other? How does that relate to the initial conditions?

Ahhh yes. That would make sense...I should have thought of that. :\

Thanks, I'll give it a go. :)

I think one of the hardest parts of physics (and science in general) is making the connection / transition between the concepts and the equations. I'd say, most people can do one OR the other; either the math, or the ideas - but its a lot harder to be able to combine the two, and find one from the other.

Good luck, Cheers!