1. Mar 29, 2012

### c0nfused34235

1. The problem statement, all variables and given/known data

I'm doing an impact physics for engineering question and I cannot tell the difference between

(v_A)_2x & (v_(Ax))_2.

* I don't think I'll need help with solving the actual question if I understand these variables.

2. Relevant equations

N/A

3. The attempt at a solution

I know that v_A is object A's initial velocity, however, I don't know how to deal with the _2x. As for the second term above, I have no idea.....

2. Mar 29, 2012

### Staff: Mentor

Welcome to the PF.

Can you post a picture or scan of the use of those symbols?

3. Mar 29, 2012

### tiny-tim

welcome to pf!

hi c0nfused34235! welcome to pf!

(try using the X2 button just above the Reply box )

you mean (vA)2x & (vAx)2 ?

what is the context?

4. Mar 30, 2012

### c0nfused34235

Hi guys, thanks for the warm welcome and quick replies. Here's the question and it's solution. I was trying to figure it out (how they solve it) and I could not understand how they found the 2 variables in the red box (see image attached below). Thanks again.

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5. Mar 30, 2012

### Staff: Mentor

(v_A)2 is the final velocity of body A, i.e., its velocity after the collision

(v_A)_2x is the x-component of body A's final velocity after collision

(v_(Ax))_2 is the after collision value of A's x-component of velocity

The sum of the x-components of momentum of the system before and after the bodies collide remains constant. The same goes for the y-components of momentum.

6. Mar 30, 2012

### tiny-tim

hi c0nfused34235!
(vA)2x and (vAx)2 are the same

(i've no idea why they've done that )

so they just add (vA)2x + (vB)2x to (vA)2x - (vB)2x to get 2(vA)2x

(and subtract to get 2(vB)2x)

7. Mar 30, 2012

### c0nfused34235

Could someone please solve for one of them (with steps)? I still don't understand how they solve for those variables. If they are indeed identical, why can't I substitute one set into the other formula? I get completely incorrect values.

Last edited: Mar 30, 2012
8. Mar 30, 2012

### c0nfused34235

YES I GOT IT!!!