Help with kinetics and conservation problem thanks

AI Thread Summary
In the discussion about a collision between two objects, the focus is on determining the velocities after the collision using conservation laws. For the first scenario, three conservation equations for momentum exist in three dimensions, but they are insufficient to solve for the six unknown velocities without additional information. In the second scenario, if kinetic energy is also conserved (elastic collision), an additional equation is available, making it possible to solve for the unknowns if one more piece of information is provided. In the third scenario, where the objects stick together (inelastic collision), momentum conservation still applies, but the system can be simplified, potentially allowing for a solution with the existing equations. Overall, understanding the conservation principles is crucial for solving the collision problem effectively.
CarlosPacheco
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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.
 
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What do you think the answers are and what are equations?
 
the question are the 1-2-3 listed there... I don't understand the question. also, my professor likes to write a lot as you can see
=S
 
CarlosPacheco said:
the question are the 1-2-3 listed there... I don't understand the question. also, my professor likes to write a lot as you can see
=S

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)
 
rock.freak667 said:
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)

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

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?
 
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