What are the forces and moments in this scenario? confused

In summary, the reaction forces and moments at the rod ends are:-Z reaction force at rod end A = -Fapplied force-Z reaction force at rod end B = Fapplied force-Bending moment at rod end A = maA-Bending moment at rod end B = maB-Torsion at rod end A = -TwA-Torsion at rod end B = -TwB
  • #1
physicsdumby
4
0

Homework Statement


A cylinder with two rods coming out of it. The ends of the rods are fixed. A force is applied through the center of the top surface of the cylinder. What are the reaction forces and moments at the rod ends?

Here is a diagram of the scenario: http://www.imgur.com/Tsdhmzf.jpg

Homework Equations

The Attempt at a Solution


I don't have exact dimensions and forces because this is a conceptual question. From what I can process, the applied force at the cylinder will cause reaction forces in the Z-direction at both rod ends. The rods will also have reaction bending moments and torsion as well? Summing moments forces and moments about one of the rod ends gave me 3 equations with 4 unknowns. Is this a statically indeterminate problem?
 
Physics news on Phys.org
  • #2
Suppose there were only one rod. Could the system be stable (theoretically)?
 
  • #3
haruspex said:
Suppose there were only one rod. Could the system be stable (theoretically)?
With just one rod, the vertical reaction force at the rod end will be equal (and opposite) to the applied force. The bending moment will be equivalent to the moment arm (distance from center of cylinder to rod end) times the applied force. No torsion in this case.
 
  • #4
physicsdumby said:
With just one rod, the vertical reaction force at the rod end will be equal (and opposite) to the applied force. The bending moment will be equivalent to the moment arm (distance from center of cylinder to rod end) times the applied force. No torsion in this case.
Sure, but could it be stable?
If so, the other rod is redundant. This means it is impossible to tell how the load is distributed between them without considering how the rods deform.
A simple assumption would be that the rods behave identically, so symmetry is preserved. For small deformations, there will be no torsion. Greater deformations will involve some complicated geometry.
 
  • #5
haruspex said:
Sure, but could it be stable?
If so, the other rod is redundant. This means it is impossible to tell how the load is distributed between them without considering how the rods deform.
A simple assumption would be that the rods behave identically, so symmetry is preserved. For small deformations, there will be no torsion. Greater deformations will involve some complicated geometry.
With a single rod, I don't see why it would be unstable. There are no lateral forces applied. Unless, of course, I'm overlooking something.

Under the simple assumption and thus acting in symmetry, each rod will have half of the applied force as its reaction force. I don't have a pen and paper right now but I assume setting the reaction bending moments of each rod equal to each other will give me a complete solution..
 

What are the forces and moments in this scenario?

The forces and moments in a given scenario refer to the external influences acting on an object or system, causing it to accelerate or change its state of motion. These forces and moments can be classified as contact forces (such as friction or normal force) or non-contact forces (such as gravity or electromagnetic force).

How do forces and moments affect an object or system?

Forces and moments can cause an object or system to accelerate, decelerate, change direction, or deform. They can also be balanced, resulting in no overall change in motion, or unbalanced, resulting in a net change in motion. The specific effects depend on the magnitude and direction of the forces and moments and the characteristics of the object or system.

What is the difference between forces and moments?

Forces and moments are both external influences acting on an object or system, but they have different characteristics. Forces are vectors with magnitude and direction, while moments are vectors with magnitude, direction, and a point of application. Additionally, forces cause linear motion, while moments cause rotational motion.

How are forces and moments calculated?

Forces and moments are calculated using the principles of Newton's laws of motion and the laws of conservation of energy and momentum. This involves analyzing the object or system, identifying all the external forces and moments, and using mathematical equations to determine their effects on the object or system.

What are some real-world examples of forces and moments?

Forces and moments are present in all aspects of our daily lives. Some examples include the force exerted by our muscles to move objects, the force of gravity pulling objects towards the Earth, and the moments created by torque in car engines. In nature, forces and moments play a crucial role in shaping the movement of planets, the flow of water in rivers, and the flight of birds and insects.

Similar threads

  • Introductory Physics Homework Help
Replies
14
Views
602
  • Introductory Physics Homework Help
Replies
11
Views
2K
  • Introductory Physics Homework Help
Replies
8
Views
1K
  • Introductory Physics Homework Help
Replies
1
Views
804
  • Introductory Physics Homework Help
Replies
4
Views
908
  • Classical Physics
2
Replies
47
Views
2K
  • Introductory Physics Homework Help
Replies
3
Views
892
  • Introductory Physics Homework Help
Replies
2
Views
1K
  • Introductory Physics Homework Help
Replies
17
Views
2K
  • Introductory Physics Homework Help
Replies
21
Views
3K
Back
Top