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Homework Help: Effect of a net force of zero mechanics question

  1. Jan 24, 2014 #1
    1. The problem statement, all variables and given/known data
    True or false

    If an object originally at rest is subjected to more than one non zero force but the forces sum to zero then the particle will not move.

    2. Relevant equations

    3. The attempt at a solution
    I say false I think it something to do with angular acceleration not sure though
    Other solutions would be appreciates
  2. jcsd
  3. Jan 24, 2014 #2

    Simon Bridge

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    What is Newton's 1st law?
    (Write it out completely.)

    You mentioned the possibility of rotation...
    Can a linear force cause rotation in a particle?
  4. Jan 24, 2014 #3
    New tons first law states that if the net force on an object is zero the object moves with cconstant velocity. Alternately an object at rest stays at rest or if moving moves with constant velocity unless acted on by aN unbalanced force
  5. Jan 24, 2014 #4
    So what's ur solution to the problem
  6. Jan 24, 2014 #5

    Simon Bridge

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    Reread post #3.
    Compare with post #1.

    Is the object at rest or moving at a constant velocity?
    Is it acted on by an unbalanced force?
  7. Jan 25, 2014 #6
    I think the answer is true due to the reconsideration. After post.three regarding newtons first.law
  8. Jan 25, 2014 #7
    Is it true?
  9. Jan 25, 2014 #8

    Doc Al

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    Yes. (Assuming that rotation is off the table. And even if it was a rotatable object, its center of mass would not move.)
  10. Jan 25, 2014 #9
    The reason why I had initially.said false was because there was some distinction being made from an object and a particle in mechanics so an object could receive rotation since the forces acting on it could be at different points while for a particle ths re can be no rotation since the force is applied at.the same pointe due to its size. So I had a problem figuring
    Whether the question was structured for an 'object' or a particle but both terms are used synonymously in the question.
  11. Jan 25, 2014 #10

    Simon Bridge

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    Yep - I would say there is a small ambiguity concerning what is meant by "movement" that can only be cleared up by context.

    We could have argued, for eg, that the object will have a temperature, and therefore it's component atoms are moving: if an object jiggles about at random, is it "moving"? But then, you are told that it is initially "at rest" - if it jiggles about, is it also "at rest"? In normal English usage it is possible to describe something as jiggling about while staying in the same place... but is that the same thing?

    We are told first that it is "an object" and then that it is "the particle" ... which is it?

    This kind of judgement call is quite common.
    Balance of probability is that the object continues in a state of rest - the mention of "the particle" and "at rest" (both being special-use terms in physics) being the clincher.
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