Help with kinetics and conservation problem thanks

Click For Summary

Homework Help Overview

The discussion revolves around a collision problem involving two objects in three-dimensional space, focusing on the conservation of momentum and kinetic energy. Participants are exploring how many conservation equations can be applied in different scenarios: elastic collisions, inelastic collisions, and the general case without additional information.

Discussion Character

  • Exploratory, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • Participants are attempting to determine the number of conservation equations applicable to the problem and whether those equations provide sufficient information to solve for the unknown velocities. Questions about the implications of conservation laws in three dimensions are raised, particularly regarding the number of directions in which momentum is conserved.

Discussion Status

The discussion is ongoing, with participants questioning the clarity of the original problem and the implications of conservation principles. Some guidance has been offered regarding the conservation of momentum in three dimensions, but there is no consensus on the number of equations needed or the sufficiency of the information provided.

Contextual Notes

Participants note the complexity of the problem due to the presence of six unknowns and the varying conditions of the collisions being considered. There is an emphasis on not providing direct answers, as per the forum's guidelines.

CarlosPacheco
Messages
3
Reaction score
0
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.
 
Physics news on Phys.org
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?
 

Similar threads

Conservation of Energy with Gravitational Potential Energy
  • · Replies 6 ·
Replies
6
Views
2K
A bullet collides perfectly elastically with one end of a rod
  • · Replies 21 ·
Replies
21
Views
3K
Conservation of Momentum Problem - Mechanical and Kinetic Energies
  • · Replies 2 ·
Replies
2
Views
1K
Confused about a conservation of energy problem
  • · Replies 4 ·
Replies
4
Views
2K
Challenging problem about an impact with a smooth frictionless surface
  • · Replies 55 ·
2
Replies
55
Views
6K
Elastic potential energy - different methods, different results
  • · Replies 2 ·
Replies
2
Views
1K
Solving Elastic Collision of Two Balls: Theory & Solutions
  • · Replies 15 ·
Replies
15
Views
4K
Test question: What is true for a mechanical impact?
  • · Replies 7 ·
Replies
7
Views
1K
How Do You Solve for Final Velocities in Elastic Collisions?
  • · Replies 20 ·
Replies
20
Views
3K
Conservation of momentum - with understanding
  • · Replies 2 ·
Replies
2
Views
2K