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Zack asked in Science & MathematicsPhysics · 1 year ago

Simple collision problem?

A billiard ball is shot west at 0.4 m/s. A second, identical ball is shot east at 1.9 m/s. The balls have a glancing collision, which deflects the first ball at 90 deg. and sending it north at 0.4 m/s. What is the speed of the other ball right after the collision?

1 Answer

  • 1 year ago
    Favorite Answer

    Only 'simple' when you know how to do it!

    Take east as +x and north as +y.

    To conserve momentum in the y direction, ball 2 must have a final y component of velocity= -0.4m/s.

    The ball 1 has a final x component of momentum = 0 (as it moves in the y direction).

    Applying conservation of momentum in the x direction:

    m(-0.4) + m(1.9) = m.0 + mv

    v = 1.5m/s (x component of ball 2's final velocity)

    So ball 2's speed = √(0.4² + 1.5²) = 1.55m/s

    (=1.6m/s to 2 sig. figs.)

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