Momentum of colliding billard balls

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AI Thread Summary
The discussion focuses on an elastic collision between two billiard balls of equal mass, where one ball is initially in motion and the other is at rest. The user attempts to apply the conservation of momentum to find the final speeds of both balls after the collision, using their respective angles of motion. Initial calculations yield incorrect results, prompting a request for assistance. It is noted that a simple error in digit placement led to the incorrect speed for the black ball. The conversation emphasizes the importance of careful calculations in physics problems involving momentum.
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Homework Statement



A white billiard ball with mass mw = 1.43 kg is moving directly to the right with a speed of v = 3.29 m/s and collides elastically with a black billiard ball with the same mass mb = 1.43 kg that is initially at rest. The two collide elastically and the white ball ends up moving at an angle above the horizontal of θw = 21° and the black ball ends up moving at an angle below the horizontal of θb = 69°.
http://smartphysics.com/images/content/mechanics/ch12/billiardballsnew2.png

I need to find the final speeds of the balls.


Homework Equations



Conservation of momentum

The Attempt at a Solution




What I tried already was having initial momentum equal to final momentum. And then splitting it into x and y components and solving for the unknown velocities and got 1.4 for the black one and 3.66 for the white one. I'm not sure where I went wrong. Please help.

Here is some of my work:
Since masses cancel out, I have
for X: 3.92 + 0 = Vwcos21 + Vbcos69
for y: 0 = Vwsin21 - Vbsin69
Then solved for Vb, which I got 1.4, but it's wrong.
 
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Your method is fine. You just swapped two digits in the initial velocity.
 
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