Energy and Momentum Conservation in Inelastic Car Collisions

[kenau_reveas]

Two cars, both of mass m, collide and stick together. Prior to the collision, one car had been traveling north at speed 2v, while the second was traveling at speed v at an angle phi south of east (as indicated in the figure). After the collision, the two-car system travels at speed v_final at an angle theta east of north.

 

[civil_dude]

Conservation of momentum, remember velocity is a vector quantity.

Show your work so we can determine where you need help.

 

[theskllzdatklls]

can anyone help me with the above problem? I've been trying to work it out but i can't find the answer to vfinal... or theta

 

[EthanB]

Like civil_dude said, show your work so we know where you went wrong.

Either use the velocities as vectors or break the conservation of momentum into its x and y components.

 

[theskllzdatklls]

i got the other homework problems but i don't think I'm even close for this one. the answer that i have so far for vfinal i have sqrt( (v*cos(phi))^2 + (2v - vsin(phi)^2)

but that doesn't work or feel right either. and i can't even begin to find theta

 

[EthanB]

Are you using energy conservation? The collision is inelastic. Use conservation of momentum.