# 1350Kg tuned up Civic moving at 15m/s hits a 1450Kg car moving at 12m/s

Im not really good at elastic and inelastic collisions,, can someone help me with collisions plz.

In the movie the fast and the furious, a 1350Kg tuned up Civic moving at 15m/s hits a 1450Kg car moving at 12m/s. Determine the final velocity of the cars if (a) the collision was elastic AND (b) the collision was inelastic.

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DrVirus,
you have 2 unknowns (the final velocities).

In an elastic collision, both momentum and kinetic energy are conserved. So 2 equations, fine.

In an inelastic collision, only momentum is conserved. To get the 2nd equation, you usually assume that the bodies stick together after collision.

Well, its been an hour since i posted the question. I got the first part for elastic collision right.. but the inelastic i cant solve it, can someone show me how to solve it, because then tomorrow i have a lab that has to do with collisions and i have to understand this. Thanks alot

As I said:
Momentum: pfinal=pinitial
Sticking: v1,final=v2,final=:vfinal
=>
(m1+m2)vfinal=pinitial

You have calculated pinitial in part (a), haven't you?

No, i didnt solve for Pi. i used an equation that works with elastic collision only and has to have V2 as 0. so i change the frame of reference to be 0, and changed it back after i got the answer.

pinitial=m1v1,initial+m2v2,initial

Just plug in.