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B Why is there a negative in Hooke's Law (F = -kx)

  1. Apr 2, 2016 #1
    For Hooke's Law, why is there a negative in F = -k*x? Is it because k is the reaction force against the force applied on the spring and not the force pushing or pulling on it? For example, let's say that the origin is set where the spring ends when it's in equilibrium with no forces applied to it. However, when I push on to it, that force is going left into the negative direction, but the reaction force to that is pointing the positive direction (right). Therefore, is the reason why there's a negative in the Hooke's Law equation is to calculate for the reaction force while giving it less thought on where is the action force is going?
  2. jcsd
  3. Apr 2, 2016 #2


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    Staff: Mentor

    That's right. The force of the spring on whatever is pulling/pushing it is always directed opposite to the displacement.
  4. Apr 2, 2016 #3
    Thank you very much for your speedy reply.
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