Basic mechanics question -- Two cables supporting a stage light

AI Thread Summary
The discussion revolves around a mechanics problem involving two cables supporting a stage light. The user is trying to determine the force in one of the cables, knowing the solution is 120N in the opposite direction to the weight of the light. Despite attempts using scale drawings and vector methods, the user struggles to arrive at this solution. A hint suggests considering the sum of all forces to find the resultant force needed. The user ultimately expresses gratitude for the assistance received.
Krashy
Messages
30
Reaction score
5

Homework Statement



Unbenannt.png


Homework Equations


[/B]
apparently none

The Attempt at a Solution


[/B]
Hi, this is a question from the OCR for self studying purposes. Only the first question is relevant for me. I know that the solution is 120N in the opposite direction to the weight, but i can't get to this solution. There is no calculation in the solution so i tried doing it with scale drawing and the head to tail method, but it didnt work. I also tried to multiply the 120N by the stage light with the cosine of the angle between the vectors but the angles are above 90 degrees so i won't get a useful solution.

All the other questions in that topic were really easy so i guess its something fairly simple that i need to do. I hope someone can help me. Thank you very much in advance.
 

Attachments

  • Unbenannt.png
    Unbenannt.png
    17 KB · Views: 1,086
Physics news on Phys.org
Hi Krashy and welcome to PF.

What is the sum of all the forces? Hint: Note that the resultant that you seek, when added to the 120 N down, should give you that sum.
 
  • Like
Likes Krashy
I got it, thanks again
 
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