Solving Pulley Problem: Find T1, T2, W1, W2, Alpha

  • Thread starter Thread starter ana111790
  • Start date Start date
  • Tags Tags
    Pulleys
AI Thread Summary
The discussion focuses on solving a physics problem involving a patient's leg supported by two weights connected through cables. The leg's weight is given as 300N, with specific distances and angles provided for calculations. The user has attempted to set up equations based on the sum of forces and moments for equilibrium but is unsure about the accuracy of their equations. They are advised to revise their force equations and include an equation for horizontal forces, while also considering Newton's third law for clarity. The key takeaway is the need for five equations to solve for the five unknowns in the problem.
ana111790
Messages
41
Reaction score
0

Homework Statement


A patient's leg is held in position by 2 weights tht are connected through cables. The weight of the leg is W = 300N. L is the horizontal distance between the points where the cables connect with the leg (points A and B) and C is the center of gravity for the leg, located 2/3 L away from A. The angles from cable 2 is Beta=45 degrees.
Find T1, T2, W1, W2, and the angle Alpha for the leg to stay in equilibrium.
[PLAIN]http://img820.imageshack.us/img820/2055/drawing5.jpg


Homework Equations


Sum of Fy=0
Sum of Fx=0
Sum of Moments = 0

The Attempt at a Solution



So I separated the pulleys, so have for the weight and pulleys on left:
Sum of Fy= T1-W1=0
For the weight and pulleys on right:
Sum of Fy=T2-W2=0 (is this correct? What is the effect of the second pulley on the tension?)

Sum of Fy= T1sin(Alpha) - W +T2sin(45)
(Should these be T1sin and T2 sin or just T1 and T 2?)

Then I did sum of moments:
Sum of moments around point A = -W*2L/3 + T2sin(45)*L=0
Sum of moments around C = -T1sin(Alpha)*2L/3 + T2sin(45)*L/3
Sum of moments around B = W*L/3 + T1sin(Alpha)*L

So basically I'm stuck. Not sure if so far it's correct of how to proceed.
 
Last edited by a moderator:
Physics news on Phys.org
Can anyone help me out? Please.
 
You have 5 unknowns so you will need 5 equations. Your moments all look okay to me, but your forces need some revision. You need to revise your Fy equation, and create an equation for Fx. Remember to use Newton's 3rd law to work out any kinks.
 
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