# physics help?

1. A billiard ball moving at 2.2 m/s strikes a second billiard ball at rest and continues at 45° from its original direction, while the other moves at −45° from the same original direction. Both billiard balls have the same mass. Find the speed of the second billiard ball.

0.78 m/s

1.1 m/s

1.6 m/s

3.1 m/s

### 1 Answer

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- WhomeLv 71 month agoFavorite Answer
conservation of momentum in the direction perpendicular to the original direction.

m(0) = mv₁sin45 + mv₂sin-45

0 = v₁sin45 + v₂sin-45

v₁sin45 = v₂sin45

v₁ = v₂

conservation of momentum in the original direction

m(2.2) = mv₁cos45 + mv₂cos-45

2.2 = v₁cos45 + v₂cos-45

as cos 45 = cos-45 and v₁ = v₂

2.2 = 2v₁cos45

v₁ = v₂ = 1.5556349... m/s

which will round to

v = 1.6 m/s

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