# Two masses coalesce into one body during collision

Yaseen

## Homework Statement

Question: A body of mass M1=m moving with a velocity V1=v in the x-direction collides with another body of the same mass m2=m moving in the y-direction with the same speed V2=v The coalesce into one body during collision

## Homework Equations

(a) Find the magnitude of the momentum of the composite body
(b)The angle which the direction of the momentum vector of the composite body makes with the x-axis
(c) The fraction of the kinetic energy transformed into heat during collision

## The Attempt at a Solution

For finding the momentum is it Just P=mv ?
I don't know the formula for finding the direction of momentum
and, Do we use the formula K.E=1/2 mv^2 or K.E=1/2 Iw^2

I Have high expectations and Hopes from this website :)

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Ray Vickson
Homework Helper
Dearly Missed

## Homework Statement

Question: A body of mass M1=m moving with a velocity V1=v in the x-direction collides with another body of the same mass m2=m moving in the y-direction with the same speed V2=v The coalesce into one body during collision

## Homework Equations

(a) Find the magnitude of the momentum of the composite body
(b)The angle which the direction of the momentum vector of the composite body makes with the x-axis
(c) The fraction of the kinetic energy transformed into heat during collision

## The Attempt at a Solution

For finding the momentum is it Just P=mv ?
I don't know the formula for finding the direction of momentum
and, Do we use the formula K.E=1/2 mv^2 or K.E=1/2 Iw^2

I Have high expectations and Hopes from this website :)
Momentum is a vector, and total momentum (the vector) is preserved in the collision.

Yaseen
Momentum is a vector, and total momentum (the vector) is preserved in the collision.
So this means that the (vector) momentum has no magnitude ?
I'm really a noob at doing vectors its a very hard concept for me !

berkeman
Mentor
So this means that the (vector) momentum has no magnitude ?
I'm really a noob at doing vectors its a very hard concept for me !
Vectors have a magnitude and a direction. In this problem, it is probably easiest to use rectangular coordinates. Can you write the equations for the initial momentum vectors of each of the masses before the collision? Then what should you write next? Yaseen
Vectors have a magnitude and a direction. In this problem, it is probably easiest to use rectangular coordinates. Can you write the equations for the initial momentum vectors of each of the masses before the collision? Then what should you write next? Momentum=Mass * velocity
P=mv
(m1+v1)+(m2+v2)=(m1+v1)+(m2+v2) (LHS)--Intial=final--(RHS) Conservation of momentum
Initial momentum equ. (m1+v1)+(m2+v2)initial
Ok so is this the equation ? I really hope so !
And Is this the equation to find the magnitude of momentum ?

Ray Vickson
Homework Helper
Dearly Missed
Momentum=Mass * velocity
P=mv
(m1+v1)+(m2+v2)=(m1+v1)+(m2+v2) (LHS)--Intial=final--(RHS) Conservation of momentum
Initial momentum equ. (m1+v1)+(m2+v2)initial
Ok so is this the equation ? I really hope so !
And Is this the equation to find the magnitude of momentum ?
Your equations are all wrong. You start by saying P = mV (and that is OK)l but then you take (m1+v1) and (m2+v2), which makes no sense (and is "dimensionally" wrong: you cannot add "kg" to "m/sec" for example).

Yaseen
Your equations are all wrong. You start by saying P = mV (and that is OK)l but then you take (m1+v1) and (m2+v2), which makes no sense (and is "dimensionally" wrong: you cannot add "kg" to "m/sec" for example).
I equated P(initial)=P(final) that's conservation of momentum right?
m1=mass of body one v1=velocity of body one
m2=mass of body 2 v2=velocity of body 2

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Ray Vickson
Homework Helper
Dearly Missed
I equated P(initial)=P(final) that's conservation of momentum right?
m1=mass of body one v1=velocity of body one
m2=mass of body 2 v2=velocity of body 2
No, you did NOT do that: m1+v1 is not the momentum of body 1 and m2+v2 is not the momentum of body 2. You need to be careful about what you write down. You will get correct answers if you use correct formulas, but will get nonsense if you write formulas that make no sense and have no basis in physics.

Yaseen
No, you did NOT do that: m1+v1 is not the momentum of body 1 and m2+v2 is not the momentum of body 2. You need to be careful about what you write down. You will get correct answers if you use correct formulas, but will get nonsense if you write formulas that make no sense and have no basis in physics.
Ok now I feel hopeless can you please guide me before atleast I had some confidience that I can do it but now I feel really disappointed that I cant do anything please can you guide me

berkeman
Mentor
Remember that momentum is a vector, and in rectangular coordinates it has an x and a y component. One way to write that is like this:

P1 = [P1x, P1y] = [M1V1x, M1V1y]

Now can you write the equations for the momenta of the individual particles as 2-D vectors (like I did above) before and after the collision? It's important that the particles are moving in different directions before the collision, and in the same direction after the collision...

• Yaseen
Yaseen
Remember that momentum is a vector, and in rectangular coordinates it has an x and a y component. One way to write that is like this:

P1 = [P1x, P1y] = [M1V1x, M1V1y]

Now can you write the equations for the momenta of the individual particles as 2-D vectors (like I did above) before and after the collision? It's important that the particles are moving in different directions before the collision, and in the same direction after the collision...
Ok yeah that was my mistake insted of taking it like Mx and My I took it as M1 and M2 ok so this is the initial step then after equating momentum before collision and after collision what do I do ?

berkeman
Mentor

## Homework Statement

Question: A body of mass M1=m moving with a velocity V1=v in the x-direction collides with another body of the same mass m2=m moving in the y-direction with the same speed V2=v The coalesce into one body during collision

## Homework Equations

(a) Find the magnitude of the momentum of the composite body
(b)The angle which the direction of the momentum vector of the composite body makes with the x-axis
(c) The fraction of the kinetic energy transformed into heat during collision
You work through the questions. Do you know how to find the magnitude and direction of a vector in rectangular coordinates?

• Yaseen
Yaseen
You work through the questions. Do you know how to find the magnitude and direction of a vector in rectangular coordinates?
No I dont know how to find the magnitude as I'm stated above I really a noob at vectors

Yaseen
You work through the questions. Do you know how to find the magnitude and direction of a vector in rectangular coordinates?
Is it the same formula used to find the magnitude of unit vectors ?

berkeman
Mentor
No I dont know how to find the magnitude as I stated above I really a noob at vectors
What class is this for? What textbook are you using, or what learning resources do you have as part of this class?

• Yaseen
Yaseen
What class is this for? What textbook are you using, or what learning resources do you have as part of this class?
This for the cbse syllabus from the JEE questions for class XI india (I'm from india)

Yaseen
This for the cbse syllabus from the JEE questions for class XI india (I'm from india)
Actually this is the homework given to me and our teacher selects the hardest questions of all for us !

Yaseen
What class is this for? What textbook are you using, or what learning resources do you have as part of this class?
This is for class XI JEE paper CBSE, I use the NCERT books as a resource

Yaseen
Special thanks to @berkeman for helping out I got it its 1/2mv*2

• berkeman