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Acceleration and Velocity

  1. May 17, 2005 #1
    I can't belive I don't remember this. Is it possible to move upwards with a constant velocity? For example, if a block weighs 20 newtons, and I want it to go at a constant velocity of 5 m/s , could I do that with a constant force? For some reason I don't think I can, but maybe I'm just screwing myself up somewhere...
  2. jcsd
  3. May 17, 2005 #2


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    Force= mass times acceleration. In order that something move with constant velocity it is necessary that the acceleration be 0 and so that the net force be 0. If an object weight 20 N. that means that there is a force of 20 Newtons downward. To balance that and get a net force of 0, you need an upward force of 20 N also. Notice that the "5 m/s" doesn't come into that. In order to move an object weighing 20 N upward at 5 m/s you must first apply a force greater than 20 N upward so there is an acceleration upward. When the speed gets to 5 m/s then you must reduce the upward force to exactly 20 N to keep that constant speed.
  4. May 17, 2005 #3


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    Incidentally,your case would work out fine,if you were to drag the body with a constant force which would balance the friction force perfectly (i.e.no vertical movement).

  5. May 17, 2005 #4


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    The amount of force needed to move upwards at constant velocity is the weight of the object.
  6. May 18, 2005 #5
    as u go further away from the earth surface the gravitaional force will continously reduce .so even if u were to ignore the intial extra force applied there would still be an accelleration whose rate would increase the further u went from the earth
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