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Homework Help: Direction of concurrent velocity and acceleration

  1. Mar 30, 2016 #1
    • Member advised to use the formatting template for questions posted to the homework forums
    I have a problem in one my dynamics classes, I have a the velocity and accelerations of two points that are constrained to vertical motion.

    Point A has a velocity of 1m/s upwards and is decelerating at a rate of 4m/s2 and point B has a velocity of 2m/s downwards and is accelerating at 5m/s2.

    Now, I need to draw these in vector form. So I am trying to interpret this information as it is quite confusing to me.

    A obviously has a velocity vector straight upwards, but the acceleration vector which is decelerating, is this pointing downwards?

    B's velocity vector is downwards, and it is said to be accelerating, so I'm assuming that this means that it is accelerating in the direction of the velocity vector, so also downwards.

    Is this the correct way to interpret this situation?

  2. jcsd
  3. Mar 30, 2016 #2


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    Your interpretation is probably correct, but I agree it is confusing. If it had said the velocity is -2m/s and the acceleration is +5m/s2 I would say it is getting slower. If it had said the velocity is 2m/s down and it is getting faster at 5m/s2 then it is accelerating downwards. But saying that it is accelerating at 5m/s2 without making clear which way is positive is somewhat ambiguous.
  4. Apr 7, 2016 #3
    The problem is stated poorly. Let's assume that all the pertinent information is stated. Then point A is traveling upward and is decelerating or slowing. In 0.25 seconds the velocity will reach zero. Velocity points up, acceleration points down. Point B is less ambiguous, both vectors point down.

    Best I can do.
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