Finding the sag caused by a weight in an equilibrium?

In summary, the student attempted to solve the equation for the sag caused by the two cylinders, but ran into trouble with the fourth degree equation.
  • #1
AObeid
2
0

Homework Statement


Hello there, this is my first thread here !
I've been trying to solve an exercise from my statics course and just couldn't get anywhere.
Basically it's a system of two springs connected by a rope, and each spring is attached to a cylinder (Both Cylinders have same mass).
The question is on question number 2 in the attached file, it requires that we calculate the sag caused by the two cylinders when they weigh 40N each.(Stiffness has been already calculated from question #1)
The attachment also views the lengths given by the problem
Here's a thumbnail of the problem
Capture.PNG

Homework Equations


Well it's equilibrium so no other equations than ΣF=0
Pythagorus in a right triangle
Hook's law T=k∇
Some trigonometry..

The Attempt at a Solution


I managed to solve easily question #1, basically from the length given and the sag caused by the cylinders, I calculated both the unstretched and the final length of one of the springs. Then I calculated the tension in that cylinder in terms of k, did summation of forces on the y-axis and managed to find the stiffness.
But the problem is with the second question. Now First I calculated the displacement of the spring in terms of the sag s, the angles in terms of s (some pythagorus done there), then I applied equilibrium. Then I got to an equation involving only the unknown sag s but it was an equation of 4th degree so that sounded absurd..
Am I missing something here? Is there an easy way behind all the messy calculation that should be done here ?
 
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  • #2
AObeid said:

Homework Statement


Hello there, this is my first thread here !
I've been trying to solve an exercise from my statics course and just couldn't get anywhere.
Basically it's a system of two springs connected by a rope, and each spring is attached to a cylinder (Both Cylinders have same mass).
The question is on question number 2 in the attached file, it requires that we calculate the sag caused by the two cylinders when they weigh 40N each.(Stiffness has been already calculated from question #1)
The attachment also views the lengths given by the problem
Here's a thumbnail of the problem
View attachment 89748

Homework Equations


Well it's equilibrium so no other equations than ΣF=0
Pythagorus in a right triangle
Hook's law T=k∇
Some trigonometry..

The Attempt at a Solution


I managed to solve easily question #1, basically from the length given and the sag caused by the cylinders, I calculated both the unstretched and the final length of one of the springs. Then I calculated the tension in that cylinder in terms of k, did summation of forces on the y-axis and managed to find the stiffness.
But the problem is with the second question. Now First I calculated the displacement of the spring in terms of the sag s, the angles in terms of s (some pythagorus done there), then I applied equilibrium. Then I got to an equation involving only the unknown sag s but it was an equation of 4th degree so that sounded absurd..
Am I missing something here? Is there an easy way behind all the messy calculation that should be done here ?
It's very hard to say. All you have given us to work with is, "I must have done something wrong." You probably did, but we can't say for sure if you don't post your work.

BTW, it's "Pythagoras".
 
  • Like
Likes AObeid
  • #3
image.jpg
This is what I've done so far.. Question #2 of course.. Sorry not sure why it's rotated though ._.
 

Related to Finding the sag caused by a weight in an equilibrium?

1. What is the equation for calculating sag caused by a weight in an equilibrium?

The equation for calculating sag is s = (Wl^2)/(8T), where s is the sag, W is the weight of the object, l is the length of the cable or wire, and T is the tension in the cable or wire.

2. How does the weight of the object affect the sag in an equilibrium?

The weight of the object has a direct impact on the sag in an equilibrium. As the weight increases, the sag also increases. This is because the weight creates a downward force on the cable or wire, causing it to stretch and sag under the tension.

3. What is the significance of finding the sag caused by a weight in an equilibrium?

Finding the sag caused by a weight in an equilibrium is important in various engineering and construction applications. It helps determine the amount of tension and support needed for cables or wires to prevent them from breaking or sagging too much. It also helps in calculating the maximum load that a structure can bear.

4. How does the length of the cable or wire affect the sag in an equilibrium?

The length of the cable or wire also has a direct impact on the sag in an equilibrium. As the length increases, the sag also increases. This is because a longer cable or wire has more surface area to stretch and sag under the weight and tension.

5. What factors can affect the accuracy of calculating the sag caused by a weight in an equilibrium?

There are several factors that can affect the accuracy of calculating the sag caused by a weight in an equilibrium. These include variations in tension, temperature, and material properties of the cable or wire. Other external factors such as wind or vibrations can also affect the sag. It is important to consider and account for these factors when performing calculations.

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