Internal Forces (Engineering Mechanics)

In summary, the problem says that the radius of each pulley must be 7.2 in, but neglecting friction, the internal forces at point J of the frame will be greater. Finally, someone needs to give an idea on how to do this problem.
  • #1
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problem says knowing radius of each pulley to be 7.2 in, neglect friction, find internal forces at point J of the frame.

1st question that I have is whether the tension in section C-E of the cable also 90 lb? how about section C-D. Also, in my diagram of each of the members, I don't know how to label forces at point E where two long members and the pulley meet.

Finally, can someone gimme an idea how to go about doing this problem?
http://img487.imageshack.us/img487/8272/15am.jpg [Broken]
http://img487.imageshack.us/img487/4066/14ch.jpg [Broken]
 

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  • #2
Are points J and K joints? I think they are assuming pulleys have mass.
 
  • #4
Yes, I'm familiar with internal forces [resultants of the stresses] (axial, shear and flexionant moment). First is to find the reactions and simply cut BE member at J, and solve for the shear force and flexionant moment.
 
  • #5
I believe you don't need to take pulleys into consideration you just find all the force around the member where point J is.
Then you just cut at point J and calculate everything again
 
  • #6
I'm having trouble finding the vertical component of the force acting on frame B...any ideas? I set the moment about A zero and I was able to find the horizontal component of the force acting on frame B.
 
  • #7
Find the joint forces (E point) on the AE member then use them to find the vertical component of the reaction at B on the BE member.
 
  • #8
I got 45 lb for the vertical component of the reaction force. is that right? :confused:
 
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What are internal forces in engineering mechanics?

Internal forces in engineering mechanics refer to the forces that act within a body or structure, causing it to deform or change shape. These forces can be either tensile (pulling) or compressive (pushing).

How are internal forces different from external forces?

Internal forces act within a body, while external forces act on the surface of the body. External forces can cause a body to move or accelerate, while internal forces only cause it to deform.

What are the types of internal forces?

The two main types of internal forces are axial forces and shear forces. Axial forces act along the longitudinal axis of a body and can be either tensile or compressive. Shear forces act perpendicular to the longitudinal axis and can cause a body to twist or bend.

How do internal forces affect the stability of a structure?

Internal forces are important in determining the stability and strength of a structure. They must be carefully considered in the design process to ensure that a structure can withstand the expected loads and forces without collapsing or failing.

How can internal forces be calculated?

Internal forces can be calculated using equations from engineering mechanics, such as the equations of equilibrium and the equations of motion. These calculations take into account the geometry, materials, and external forces acting on a structure.

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