What are the Equilibrium Conditions for a 3D Rigid Body with Applied Forces?

In summary, the rod assembly shown has a ball-and-socket joint at A and a smooth journal bearing at C. Four forces are applied at points A and C with given magnitudes and the geometry of the rod assembly is also specified. The homework problem involves determining the magnitude of various reaction forces at points A, B, and C. The equations used to solve the problem are sum of moments and sum of forces, with 6 unknown reaction forces and 6 equilibrium equations. It is important to sum moments about axes rather than points. The process may be time-consuming, as evidenced by the person working on the problem for 7 hours.
  • #1
KiltedEngineer
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Homework Statement



The rod assembly shown has a ball-and-socket joint at A and a smooth journal bearing at C. The forces F1=600N , F2=410N , F3=460N , and F4=950N are applied as shown in the figure. The geometry of the rod assembly is given as a=0.900m , b=0.650m , and c=0.800m. Neglect the weight of the rod. The journal bearing supports the rod in such a manner that it is free to rotate about the y axis.

1.)Determine the magnitude of the y component of the reaction at C

2.) Determine the magnitude of the z component of the reaction exerted on the rod at C.

3.) Determine the magnitude of the z component of the reaction on the rod at B.

4.) Determine the magnitude of the x component of the reaction on the rod at B.

5.) Determine the magnitude of the z component of the reaction on the rod at A

6.) Determine the magnitude of the x component of the reaction on the rod at A

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  • #2
You have 6 unknown reaction forces and 6 equilibrium equations. Can you set those up?
 
  • #3
When summing moments = 0, sum about axes, not points. Like
Sum of moments about z axis = sum of F_x(y) + F_y(x) , where y and x are the perpendicular distances from the line of action of F_x and F_y respectively, to the z axis. Etcetera for other axes with appropriate subscripts. 7 hours, those were the days my friend I'd thought they'd never end...
 

1. What is 3D Rigid Body Equilibrium?

3D Rigid Body Equilibrium is a concept in physics that refers to the state of an object when all forces acting on it are balanced, resulting in no net motion or rotation.

2. How is 3D Rigid Body Equilibrium different from 2D Rigid Body Equilibrium?

3D Rigid Body Equilibrium takes into account forces acting in all three dimensions (x, y, and z), while 2D Rigid Body Equilibrium only considers forces in the x and y directions.

3. What are the conditions for 3D Rigid Body Equilibrium?

In order for a 3D rigid body to be in equilibrium, the sum of all forces acting on it must equal zero and the sum of all torques (rotational forces) must also equal zero.

4. How can 3D Rigid Body Equilibrium be applied in real-life situations?

3D Rigid Body Equilibrium can be used to analyze and predict the behavior of objects in various scenarios, such as bridges, buildings, and other structures. It is also used in fields like engineering and biomechanics.

5. What are some common techniques used to solve problems involving 3D Rigid Body Equilibrium?

Some common techniques include resolving forces and torques into their components, using free body diagrams, and applying the equations of static equilibrium (sum of forces = 0 and sum of torques = 0).

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