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

1. Nov 2, 2003

DrVirus

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.

Last edited by a moderator: Feb 7, 2013
2. Nov 2, 2003

arcnets

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.

3. Nov 2, 2003

DrVirus

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

4. Nov 2, 2003

arcnets

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?

5. Nov 2, 2003

DrVirus

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.

6. Nov 2, 2003

arcnets

pinitial=m1v1,initial+m2v2,initial

Just plug in.