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Achieve a state of static equilibrium

  1. Mar 25, 2012 #1
    1. The problem statement, all variables and given/known data
    If a body is acted upon by clockwise moments of 75 N at 1.25 m
    And anticlockwise moments of 50 N at 1.3 m ,
    Is it in a state of static equilibrium ?
    If not what is required to achieve a state of static equilibrium ?

    2. Relevant equations
    sum of all forces on all particles of the system is zero ...

    3. The attempt at a solution
    Should I increase the 50 N to be 75 N , Then level the distance to get the equilibrium ?
    I really don't know What/How to solve this , Please guide me through ,
    Your helping efforts are Highly needed and appreciated .
  2. jcsd
  3. Mar 25, 2012 #2
    That is one way, but i think the idea is to calculate the torque needed to obtain equilibrium, and since they act from different distances you would write something like:
    [itex]\sum\tau = l_1f_1 - l_2f_2 = 0[/itex]
    and that is the condition /equation you need to solve it.
  4. Mar 25, 2012 #3
    I don't get these symbols ? more HELP please
    Please consider that I know so little, Teach me like a kid
  5. Mar 25, 2012 #4


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    Gold Member

    Do you know how to calculate a moment?
  6. Mar 25, 2012 #5
    is it force x given distance ?
    in the question it would be
    75 N X 1.25 m
  7. Mar 25, 2012 #6


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    Gold Member

    Yes. The moment about a given point is the size of the force x the perpendicular distance to that point.

    What do you know about the sum of the moments of the forces of a system that is in equilibrium?
  8. Mar 25, 2012 #7
    What is your point ?
  9. Mar 26, 2012 #8
    - No it’s not in a state of static equilibrium,
    In order for a body to be in static equilibrium
    The vector sum of the forces and torques should be zero
    Moment = force × distance
    75N × 1.25m = 93.75 Nm .
    50N × 1.3m = 65 Nm.
    Total moments= 93.75 – 65 = 28.75 N clockwise direction
    so clearly it’s not in a state of static equilibrium,
    If the perpendicular distance of the anticlockwise moment was changed to 1.875m we would then get
    50N x 1.875 = 93.75
    75N x 1.25 = 93. 75
    We now have it in a state of static equilibrium.
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