Statics example from Meriam ( SI improper )

In summary, the conversation discusses the concept of partial constraints and how they can affect the tension in a system. It is mentioned that the top of a cosine function is horizontal and that this can lead to high tension forces in a diagonal link when the body is rotated. This phenomenon is compared to using a chain to retrieve a vehicle from a ditch, where the tension in the chain increases when pulled taut. Ultimately, the conversation highlights the practical applications of understanding partial constraints in various systems.
  • #1
lakuzamalakuzam
5
0
1601627384573.png
1601627422849.png

could not understand why it is partial constraints. Also, I don't understand how link works. Below here is what I am thinking i think it is totally wrong can someone explain what's wrong with my idea here.
1601627852528.png
 
Engineering news on Phys.org
  • #2
Welcome to PF.

The blue rectangle is not fully constrained by the three links within the frame. The position of A is fixed by the first two links, but the diagonal link 3 may be stretched as the body is rotated slightly about A.

The top of the cosine function at zero, is horizontal. Because the line from A to link 3 is straight, very high tension forces could be present in link 3 if the body was rotated slightly.
 
  • Like
Likes Lnewqban
  • #3
As @Baluncore stated, the tension on link 3 goes to infinity when its attachment points are co-linear with point A. The situation is similar to a rope or chain stretched tight between two supports. Try calculating the tension when pushing on the center of the rope/chain span.

A practical use of the phenomena is retrieving a vehicle from a ditch.
Two people with a chain, a tree, and something to block the wheels, can pull the vehicle out. Providing there is a portion of the chain not being supported (by the ground):
  1. chain taught between tree and vehicle
  2. person 1 stands on the middle of the chain, deflecting it
  3. person 2 chocks the vehicle wheels so can't roll back down into the ditch
  4. person 1 steps off the chain and repeats from step (1)
Upon completion, they choose a different route. :olduhh:

Cheers,
Tom
 
  • Informative
Likes berkeman

Related to Statics example from Meriam ( SI improper )

1. What is statics and why is it important in engineering?

Statics is a branch of mechanics that deals with the study of forces and their effects on rigid bodies at rest. It is important in engineering as it helps engineers design structures and machines that can withstand external forces and remain in equilibrium.

2. What is the SI improper system of units used in statics?

The SI improper system of units is a metric system of units used in statics, which includes the meter (m) for length, kilogram (kg) for mass, and second (s) for time. It also includes the newton (N) for force and pascal (Pa) for pressure.

3. How is the concept of moment applied in statics?

The concept of moment is applied in statics to analyze the rotational equilibrium of an object. It is the product of the force and the perpendicular distance from the force to the point of rotation. Moments can be either clockwise or counterclockwise, and their sum must be equal to zero for an object to be in rotational equilibrium.

4. What is the difference between a scalar and a vector in statics?

In statics, a scalar is a physical quantity that only has magnitude, such as mass or temperature. A vector, on the other hand, has both magnitude and direction, such as force or velocity. In order to fully describe a force in statics, both its magnitude and direction must be specified.

5. How do you calculate the center of mass in statics?

The center of mass in statics can be calculated by finding the weighted average of the position of all the particles in an object. This is done by multiplying the mass of each particle by its distance from a reference point, and then dividing the sum of these products by the total mass of the object. The resulting point is the center of mass.

Similar threads

  • Atomic and Condensed Matter
Replies
3
Views
431
  • Mechanical Engineering
Replies
31
Views
2K
  • Mechanical Engineering
Replies
2
Views
1K
  • Mechanical Engineering
Replies
10
Views
6K
  • Mechanical Engineering
Replies
2
Views
380
  • Engineering and Comp Sci Homework Help
Replies
2
Views
1K
Replies
11
Views
2K
  • Mechanical Engineering
Replies
8
Views
3K
  • Mechanical Engineering
Replies
11
Views
3K
  • Programming and Computer Science
Replies
3
Views
841
Back
Top