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- Thread starter knonk
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tiny-tim

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i want to identify the direction and magnitude of V1 vertex and the V2 vertex after they collided , does anyone have some idea about this ?

Hi knonk! Welcome to PF!

(your picture doesn't show any vertex marked V1 or V2 )

Show us what you've tried, and where you're stuck, and then we'll know how to help!

- #3

knonk

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Okey, in this picture :

With :

+ V1 : initial velocity vector of Circle

+ M1 : mass of Circle

+ V2 : initial velocity vector of Rectangle

+ M2 : mass of Rectangle

i want to identify the direction and magnitude of V1 vector and the V2 vector after they collided, does anyone have some idea about this ?

With :

+ V1 : initial velocity vector of Circle

+ M1 : mass of Circle

+ V2 : initial velocity vector of Rectangle

+ M2 : mass of Rectangle

i want to identify the direction and magnitude of V1 vector and the V2 vector after they collided, does anyone have some idea about this ?

Last edited:

- #4

tiny-tim

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(ah, you meant "vector", not "vertex"!)

i want to identify the direction and magnitude of V1 vector and the V2 vector after they collided, does anyone have some idea about this ?

On this forum, the idea is that

Show us what you've tried, and where you're stuck, and then we'll know how to help!

- #5

knonk

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Please look at this picture :

First, we consider that :

How to find V1f and V2f

*Before the collision

+Momentum of the objects:

But seem they have something wrong but i don’t know,

Uhm,Hope u can tell me. Thanks alot.

First, we consider that :

+ v1i : veloc vector of circle BEFORE they collide

+ v2i : veloc vector of rectangle BEFORE they collide

+ v1f : veloc vector of circle AFTER they collide

+ v2f : veloc vector of rectangle AFTER they collide

+ v2i : veloc vector of rectangle BEFORE they collide

+ v1f : veloc vector of circle AFTER they collide

+ v2f : veloc vector of rectangle AFTER they collide

How to find V1f and V2f

*Before the collision

+Momentum of the objects:

p1i = m1*v1i

p2i = m2*v2i

Pi = p1i+p2i

+Kinetic energy of the objects:p2i = m2*v2i

Pi = p1i+p2i

ke1i = (1/2)*m1*v1i2

ke2i = (1/2)*m2*v2i2

KEi = ke1i+ke2i

*After the collisionke2i = (1/2)*m2*v2i2

KEi = ke1i+ke2i

p1f = m1*v1f

p2f = m2*v2f

Pf = p1f+p2f

+Kinetic energy of the objects:p2f = m2*v2f

Pf = p1f+p2f

ke1f = (1/2)*m1*v1f2

ke2f = (1/2)*m2*v2f2

KEf = ke1f+ke2f

*Apply the law of the conservation of momentumke2f = (1/2)*m2*v2f2

KEf = ke1f+ke2f

Pi = Pf = P

m1*v1i+m2*v2i = m1*v1f+m2*v2f

KEi = Kef

(1/2)*m1*v1i2+(1/2)*m2*v2i2 = (1/2)*m1*v1f2+(1/2)*m2*v2f2

*Rearranging and combining the two equations above, we get the following:m1*v1i+m2*v2i = m1*v1f+m2*v2f

KEi = Kef

(1/2)*m1*v1i2+(1/2)*m2*v2i2 = (1/2)*m1*v1f2+(1/2)*m2*v2f2

v1i-v2i = v2f-v1f

V = v1i-v2i

So,

v1f = v2f-V

*Using the above equation with the equation for P, we get the final results:V = v1i-v2i

So,

v1f = v2f-V

v2f = (P+V*m1)/(m1+m2)

v1f = v2f-v1i+v2i

So we know the way how to find V1f and V2f,and we have this :v1f = v2f-v1i+v2i

V1i = V1;

V2i = V2;

And m1,m2, so we can find v1f,v2f V2i = V2;

But seem they have something wrong but i don’t know,

Uhm,Hope u can tell me. Thanks alot.

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rl.bhat

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