Cables, pulleys, 2 weights

AI Thread Summary
The discussion revolves around solving a system of equations related to forces in a pulley and weight scenario. The user initially struggles to find a third equation needed to solve for angles and tensions in the system. They mention using the relationship a + b = 90 degrees but encounter errors. A suggestion is made to consider the vector addition diagram, emphasizing that the sum of vectors should form a closed polygon. The user acknowledges the advice and indicates they have resolved their confusion.
DylanMurfly
Messages
3
Reaction score
0
Homework Statement
I've been struggling with this question for a while now, and for the life of me i cant see what i'm missing, the picture is in the solution attempt along with the equations i've been using. Any assistance would be amazing. Find: Tension AB and Angle a
Relevant Equations
W1 = 330g
W2 = 440g
1713386600869.png

Fx = 0 = ABcos(a)+BCcos(b)-BDcos(30)
Fy = 0 = ABsin(a)+BCsin(b)-BDsin(30)

==

Fx = 0 = ABcos(a) + 3.2737cos(b) - 3.738
Fy = 0 = ABsin(a) + 3.237sin(b) - 2.158

But i cant find a third equation to use. I've tried a+b = 90 but that produced a number of errors. Thank you.
Edit: angle b is the angle string CB makes with horizontal
 
Last edited:
Physics news on Phys.org
Please post the question that the problem asks. What are you looking for? The homework statement must be as was given to you.
 
kuruman said:
Please post the question that the problem asks. What are you looking for? The homework statement must be as was given to you.
updated, sorry about that
 
Finding the tension AB is easy. You are missing that when the sum of N vectors is zero and you draw the vector addition diagram, the ensuing shape is a closed polygon with N sides. Apply this idea here.
 
Thank you sir, got it all fixed up now, didn't even think to go about it that way, earlier response was a brain fart as its quite early in the morning and i haven't had a coffee yet.
 
Thread 'Variable mass system : water sprayed into a moving container'

Thread 'Variable mass system : water sprayed into a moving container'

Starting with the mass considerations #m(t)# is mass of water #M_{c}# mass of container and #M(t)# mass of total system $$M(t) = M_{C} + m(t)$$ $$\Rightarrow \frac{dM(t)}{dt} = \frac{dm(t)}{dt}$$ $$P_i = Mv + u \, dm$$ $$P_f = (M + dm)(v + dv)$$ $$\Delta P = M \, dv + (v - u) \, dm$$ $$F = \frac{dP}{dt} = M \frac{dv}{dt} + (v - u) \frac{dm}{dt}$$ $$F = u \frac{dm}{dt} = \rho A u^2$$ from conservation of momentum , the cannon recoils with the same force which it applies. $$\quad \frac{dm}{dt}...
View full post »
Thread 'Minimum mass of a block'

Thread 'Minimum mass of a block'

Here we know that if block B is going to move up or just be at the verge of moving up ##Mg \sin \theta ## will act downwards and maximum static friction will act downwards ## \mu Mg \cos \theta ## Now what im confused by is how will we know " how quickly" block B reaches its maximum static friction value without any numbers, the suggested solution says that when block A is at its maximum extension, then block B will start to move up but with a certain set of values couldn't block A reach...
View full post »

Similar threads

Calculation of resulting force from out of axis Torque
Replies
21
Views
3K
What if check: Am I calculating tension wrong?
Replies
3
Views
2K
Find Theta & Mass of Box Using Forces & Pulleys
Replies
21
Views
3K
Determine the mass of an object using the angle in the system
Replies
15
Views
2K
The tension in the cord in this system
Replies
7
Views
2K
Block and pulley on movable incline
Replies
2
Views
2K
Need help with a pulley and tension problem
Replies
3
Views
2K
What is the tension in the right cable?
Replies
4
Views
2K
Static Equilibrium Two Pulleys and Weights With Ring
Replies
3
Views
5K
The relationship between angle of incline and friction force
Replies
10
Views
9K

Hot Threads

Recent Insights

Back
Top