Inelastic collision of equal masses and velocities

[Fanman22]

After a completely inelastic collision between two objects of equal mass, each having initial speed, v, the two move off with speed v/5.5. What was the angle between their initial directions?

Well, inelastic collision so it looks like I'll be using the momentum equation in here. My professor loves these "ratio-type" problems and I believe that I'll have to use something of the sort on this.

Momentum in = Momentum out
mv + mv = m(v/5.5) + m(v/5.5)

Not sure where to go from there, and I don't see how I will find an angle out of all of this. Anyone have any sugestions as to where I should start?

 

[dextercioby]

No,no,conservation of momentum is a typical example of vector relation/equation...

Sides,in the final state,there's only one particle...

Daniel.

 

[jdavel]

Fanman22,

Have you tried drawing a picture showing the particles and their directions of travel before and after the collision? If not, it might help.

 

[dextercioby]

Yeah,you'd see an isosceles triangle there.It would help you with the projection of the vector equation on some nicely chosen axis of coordinates.

Daniel.

 

[Fanman22]

*****http://img.photobucket.com/albums/v225/Fanman22/c7f601bb.jpg *****

Is that even remotely correct? I'm not sure the isosceles triangle idea makes sense to me. I don't understand how it represents the motion of the 2 particles before the collision and how it represents the velocity of the total mass afterwards.

 

[dextercioby]

Nope.It should have been more like an Y.Actually exactly like an Y...

Daniel.

 

[Fanman22]

I can see the "Y-shape" now...What I did was take the components (in the direction of the final velocity) of each V. So...

Vsin(theta) + Vsin(theta) = (v/5.5) = 2Vsin(theta)
Theta = 5.216

To find the angle between the particles...
180 - 5.216 - 5.216 = the middle angle = 169.6

But of course, I got it wrong again

Where did I go wrong?

 

[jdavel]

Fanman,

You almost have it. But what does your equation:

Vsin(theta) + Vsin(theta) = (v/5.5)

say is conserved? What's really conserved?

 

[what]

yes what jdavel said
Edit* didn't look too closely myself