EQUILIBRIUM OF RIGID BODY UNDER COPLANAR FORCES


INPUT   DATA EXAMPLE Of Input/Output

Title  

Length of beam, L1 

    

Location of hanging object, L2  m  
Location of rope-beam connection, L3  m
Height of rope anchor point, L4 
Weight of beam, Fb 
Weight of object, Fo  N  


     Reset


OUTPUT   VARIABLES   &   GRAPHS

Variables   Values   Units
 ♦  Tension in rope, Ft 
 ♦  Rope inclination angle, θ   °  
 ♦  Horizontal Reactive force at hinge, Frh  N  
 ♦  Vertical Reactive force at hinge, Frv  N  
 ♦  Resultant reactive force at hinge, Fr  N  
 ♦  Direction of resultant force at hinge, φ   °  

THEORY  &   FORMULAE

Rigid Body Equilibrium

A rigid body subjected to forces acting in a vertical plane will be equilibrium when the following two conditions are satisfied: i) vector summation of all forces must be zero, and ii) sum of all torques acting on the body must be zero. The weight of the body is assumed to act through its center of gravity.

Consider a uniform beam hinged at one end and carrying an object. A tie-rope is connected to the beam to keep it horizontal as shown. The equilibrium forces at work in the system can be described by the equations:

   tanθ = L4/L3
   Ft = [FoL2 + FbL1/2]/L3sinθ
   Frh = Ftcosθ
   Frv = Fb + Fo - Ftsinθ
   Fr = √[Frh2 + Frv2]
   tanφ = [Frv/Frh]

where
     L1 = length of beam
     L2 = horizontal distance to point of hanging object from wall
     L3 = horizontal distance to rope-beam connection point from wall
     L4 = vertical distance to rope-wall connection point from beam
     Fo = weight of hanging object
     Fb = weight of beam
     Ft = tensile force acting in tie-rope
     Frh = horizontal component of reactive force at hinge
     Frv = vertical component of reactive force at hinge
     Fr = reactive force at hinge
     θ = angle of inclination of tie-rope to the horizontal, < 90°
     φ = inclination angle of resultant force at hinge, >= -90°, <= 90°

Tips

    ◊ Use link EXAMPLE Of Input/Output  to demo data entry expectations and results; you may edit & use it as starting point

BIBLIOGRAPHY