# Help with kinetics and conservation problem thanks!

1. Jun 27, 2010

### CarlosPacheco

An object of mass m1 moving with velocity v1 in three dimensions collides with
a second object of mass m2 moving with velocity v2. We are interested in solving
for the velocities of the objects after the collision. There are six unknown values
f (v1x)f ; (v1y)f ; (v1z)f ; (v2z)f ; (v2y)f ; (v2z)f g in three dimensional.

(1) If no additional information is given, how many conservation equations
do we have? Do we have enough information to solve for the six unknown values?
If not, how many additional equations or additional pieces of information do we
need to solve for the six unknown values?

(2) If we know that the kinetic energy of the two objects is conserved (a.k.a.
totally elasticcollision), how many conservation equations do we have? Do we
have enough information to solve for the six unknown values? If not, how many
additional equations or additional pieces of information do we need to solve for
the six unknown values?

(3) If we know that the two objects are stuck together (,a.k.a. totally in-
elasticcollision) how many conservation (or other conservation-like) equations
do we have? Do we have enough information to solve for the six unknown val-
ues? If not, how many additional equations or additional pieces of information
do we need to solve for the six unknown values?

Note: do not answer this question with answers like six, yes, none. While
you do not need to write down the conservation equations, you do need to at
least mention what the equations are.

2. Jun 27, 2010

### rock.freak667

What do you think the answers are and what are equations?

3. Jun 27, 2010

### CarlosPacheco

the question are the 1-2-3 listed there... I dont understand the question. also, my professor likes to write a lot as you can see
=S

4. Jun 27, 2010

### rock.freak667

Conservation of momentum: The momentum in a given direction in a closed system is constant.

Meaning that: momentum before = momentum after in a particular direction.

So for questions 1, momentum will be conserved in how many directions given you know the above definition? (You are in 3D)

5. Jun 27, 2010

### CarlosPacheco

would be then conserved in all directions right?? X, Y and Z

6. Jun 28, 2010

### rock.freak667

Yes, but if you have 6 unknowns and 3 equations can you solve it?

Secondly, when the kinetic energy is conserved, how many equations do you now have?

Thirdly, if 2 are stuck together, how many now?