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Math Help - Impulse with wall and change of direction

  1. #1
    Super Member craig's Avatar
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    Impulse with wall and change of direction

    Got an impulse question here that I wouldn't normally struggle with, however there's something about a change of direction and not sure what to do here?

    A ball of mass 0.1 kg hits a wall at 15 m/s and rebounds at a speed of 5 m/s.

    If the path of the ball's diverted by \frac{\pi}{2} radians by the impact, find the magnitude of the impulse exerted on the ball by the wall.

    I = m(v_2 - v_1)

    I = 0.1(-5 - 15) = -20, so the magnitude of the impulse would be 20 Ns?

    Think that's right anyway. However I'm not sure how I'd solve it with the change of direction involved?

    Thanks in advance
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  2. #2
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    If you use vector subtraction, |m(v_2 - v_1)| = m\sqrt{5^2 + 15^2} since the ball bounces at a right angle. This gives the magnitude of the impulse to be [Math]1.581 N \cdot s.[/tex] I'm not sure if this is the correct way to do the problem, but it does account for the change in direction.
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  3. #3
    Super Member craig's Avatar
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    Sorry for the late reply. Thanks that makes sense, not used to dealing with vector velocities in questions like these. Thanks again!
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