# Conservation of Momentum law problem

• Quantum Fizzics
In summary, the conversation discusses the conservation of momentum and elasticity in a scenario where two objects with different masses and velocities collide. The equations for conservation of momentum and elasticity are mentioned, and a diagram is provided for reference. The conversation includes attempts at solving the problem and a question about substitution of variables. The expert summarizer explains the reasoning behind making the substitution and suggests solving the resulting quadratic equation for the final answer. The conversation ends with a clarification on the use of the term "dawg."
Quantum Fizzics

## Homework Statement

m1= 3kg m2= 6kg
v1 = 5m/s v2= 2m/s
d = 3m
DIAGRAM : http://gyazo.com/17b3126726b109256a35f65b86708bb0

## Homework Equations

Conservation of momentum:
m1+v1 = m1v1'+m2v2'

Conservation of elastic:
m1v1^2+m2v2^2 = m1v1'^2+m2v2'^2

## The Attempt at a Solution

Now my attempt was use both equations & the answers I've gotten so far are 27=3v1'+6v2'(for conservation of momentum) & the 2nd one I've got for the conservation of elastic is 99= 3v1'^2 + 6v2'^2 since they will collide at some point. The only thing I'm stuck at is what to do next afterwards. My teacher has done a similar question but I can never understand how he did it.

Is the conservattion of momentum law correct ??!
I mean Is it llike what you wrote or like the following
m1v1 + 0 = m1v1+m2v2

Zero indecates that the momentum is zero because the vilocity of the second ball before collision is zero ..
Am I right ..

Sorry v1 has a value
so the will be
m1v1 +m2v2 = m1v1+m2v2

Im just stuck because the example that my teacher gave was like "50=2(10-3v2'/2)^2+3v2'^2" that bracket part confuses me

Try to equte the two equation or write v1 in term of v2..

Maged Saeed said:
Try to equte the two equation or write v1 in term of v2..
WOW WHAT THE ****, OK I DID THAT ONE BEFORE. Its this right? " V1+V1' = V2+V2'" but can u explain why that is that cus it made some sense to me. & I showed my friend this process but, she said it made no sense so.

I think your teacher has written v1 in term of v2
try to do so from the first equation your v1 will be (27 - 6 v2) /3 which is 9-2v2

It seems reasonable
;)

Maged Saeed said:
I think your teacher has written v1 in term of v2
try to do so from the first equation your v1 will be (27 - 6 v2) /3 which is 9-2v2

It seems reasonable
;)
but why is that though? :( pls

Because v1 and v2 are related by these two equations and their value must satisfy both of them
so we make this substitution

Maged Saeed said:
Because v1 and v2 are related by these two equations and their value must satisfy both of them
so we make this substitution
alright thaanks dawg really appreciate that, last question in the example he gave so the last line was 50-50 = -30v2'+7.5v2'^2
the left side what if it wasnt 0

Last edited:
If the lift side isn't zero move it to the right side and solve the quadratic equation..

By the way what does dawg mean in your last comment

Maged Saeed said:
If the lift side isn't zero move it to the right side and solve the quadratic equation..

By the way what does dawg mean in your last comment
means like dude lol kids these days

## 1. What is the conservation of momentum law?

The conservation of momentum law is a fundamental principle in physics that states that the total momentum of a closed system remains constant over time, regardless of any internal changes or interactions within the system. This means that the total amount of momentum before an event or interaction must be equal to the total amount of momentum after the event or interaction.

## 2. How is the conservation of momentum law applied in problem solving?

In problem solving, the conservation of momentum law can be used to predict the outcome of a collision or other interaction between objects. By calculating the total momentum of the system before and after the event, one can determine the velocities and directions of the objects involved.

## 3. What are the key principles of the conservation of momentum law?

The key principles of the conservation of momentum law are that momentum is a vector quantity, meaning it has both magnitude and direction, and that the total momentum of a closed system cannot be created or destroyed, only transferred between objects within the system.

## 4. What types of systems does the conservation of momentum law apply to?

The conservation of momentum law applies to any closed system, meaning a system where there is no external force acting on the objects within it. This can include collisions between objects, explosions, and other interactions.

## 5. What are some real-life applications of the conservation of momentum law?

The conservation of momentum law has many real-life applications, including predicting the outcome of car crashes, designing spacecraft trajectories, and understanding the behavior of particles in particle accelerators. It is also an important principle in sports, such as billiards and ice skating, where collisions between objects occur.

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