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If you are told an object is accelerating what should you conclude?

  1. Sep 9, 2009 #1
    If you are told an object is accelerating, what should you conclude? Choose all that apply.

    The object is speeding up.
    The object is slowing down.
    The object is changing direction.
    There is a nonzero net force acting on the object.
    The object is moving with a constant velocity.

    Please help. I'm very confused with this question I don't understand if the object is changing direction
  2. jcsd
  3. Sep 9, 2009 #2

    sorry didn't see your note, acceleration is a vector, that means it is indeed dependant on direction.

    That means say if it's turning from north to east, (and east is where you want to go) you're going from a speed of 0 m/s towards east while going north, make sure to draw this out as you can see it clearer. You go from 0m/s east while going north to X m/s east after going through the full turn. Now imagine the actual turning, when you're at north east - 45 degrees from north you're travelling X/2 m/s. so can you see that if you're going at a speed X and turning from north -> east, because east is where you want to go (i.e posotive) you're actually accelerating in the direction of east?

    sorry i'm terrible at explaining
    Last edited: Sep 9, 2009
  4. Sep 9, 2009 #3
    Think of circular motion. The magnitude of the velocity is constant, but the direction changes => it is an accelerated motion!

    Just think about a carousel you sit in and remember the force which pushs you in the seat.

    So an accelerating object can change its direction but does not have to!

    (Originally in our world you need three components of the acceleration: the x-, y- and the z-component to answer your question sufficient!)
  5. Sep 9, 2009 #4
    Hi there,

    When talking about the acceleration of an object, in physics, you must look the vectoriel acceleration, and not only the magnitude. Therefore, an object that changes direction will have a variation in the vector velocity over a certain period of time, therefore an acceleration.

    To induce any acceleration, you must have an external acting upon the object.

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