Finding the sag caused by a weight in an equilibrium?

AI Thread Summary
The discussion revolves around a statics problem involving two springs and cylinders, where the goal is to calculate the sag caused by the weight of the cylinders, each weighing 40N. The user successfully solved the first part of the exercise but struggles with the second question, which leads to a complex fourth-degree equation for sag. They express confusion about whether they missed a simpler method or made an error in their calculations. The conversation emphasizes the need for clarity in the user's calculations to identify any mistakes. Overall, the thread highlights the challenges of applying equilibrium and trigonometric principles in statics problems.
AObeid
Messages
2
Reaction score
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 ?
 
Physics news on Phys.org
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
image.jpg
This is what I've done so far.. Question #2 of course.. Sorry not sure why it's rotated though ._.
 
I multiplied the values first without the error limit. Got 19.38. rounded it off to 2 significant figures since the given data has 2 significant figures. So = 19. For error I used the above formula. It comes out about 1.48. Now my question is. Should I write the answer as 19±1.5 (rounding 1.48 to 2 significant figures) OR should I write it as 19±1. So in short, should the error have same number of significant figures as the mean value or should it have the same number of decimal places as...
Thread 'A cylinder connected to a hanging mass'
Let's declare that for the cylinder, mass = M = 10 kg Radius = R = 4 m For the wall and the floor, Friction coeff = ##\mu## = 0.5 For the hanging mass, mass = m = 11 kg First, we divide the force according to their respective plane (x and y thing, correct me if I'm wrong) and according to which, cylinder or the hanging mass, they're working on. Force on the hanging mass $$mg - T = ma$$ Force(Cylinder) on y $$N_f + f_w - Mg = 0$$ Force(Cylinder) on x $$T + f_f - N_w = Ma$$ There's also...
Back
Top