Wire tension and motion in a pulley system

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Homework Help Overview

The discussion revolves around a physics problem involving a pulley system with two individuals, Joey and Caitlin, connected by a wire. The problem requires analyzing the forces acting on each individual and understanding the implications of motion within the system.

Discussion Character

  • Exploratory, Conceptual clarification, Mathematical reasoning, Problem interpretation

Approaches and Questions Raised

  • Participants explore the forces acting on Joey and Caitlin, questioning how these forces relate to the tension in the wire and the motion of the system. There are discussions about applying Newton's laws to derive equations for tension and acceleration, as well as the implications of Caitlin's inability to exert force on external objects.

Discussion Status

The discussion includes attempts to derive equations for tension and acceleration, with some participants providing insights into the relationships between the forces and motions involved. There is a recognition of the internal forces at play and how they affect the system, but no consensus has been reached on the final calculations or interpretations.

Contextual Notes

Participants note the constraints of the problem, including the specific masses and weights of Joey and Caitlin, and the assumption that Caitlin cannot touch anything other than the rope. There is also mention of the calculated acceleration, which may influence the understanding of the tension in the wire.

mezmorize
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Hello everyone, i need help with these 2 question from physics. I am a year 11 physics student.

Joey and Caitlin hang from two ends of a wire, looped through an ideal pulley. Joey has a mass of 75.0Kg, whilst Caitlin weighs 637N.

a) calculate the tension of the wire?

b) If Caitlin is not able to reach out and touch anything, is she able to change the motion of the system? Why?
 
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mezmorize said:
a) calculate the tension of the wire?

What forces act on which of them? In this case, it's easy to determine directions of their motion and calculate acceleration.

mezmorize said:
b) If Caitlin is not able to reach out and touch anything, is she able to change the motion of the system? Why?

Some kind of force is required to change the motion of the system. Now, is there any way to obtain that force if Caitlin can't touch anything (just remember the definition of force)?
 
a) From Newton 2nd law applied to catlin and joey we get the following two equations.
[tex]W_C-T=m_Ca_C[/tex]
[tex]W_J-T=m_Ja_J[/tex] where T is the tension of the wire. All you need to do is solve this system of equations for T, given that [tex]a_C=-a_J[/tex] where minus sign comes from fact that they ll move in opposite direction(if one is going up the other will go down).

b) If caitlin is not able to reach out and touch anything except the rope, then the only force that caitlin can exert is to Joey through the rope. But then due to Newtons 3rd Law, Joey will exert an equal but opposite force to caitlin. Because caitlin and joey are connected with the rope, this internal force cannot change the motion of neither of them, neither the motion of the rope, it just increases the tension of the rope.
 
Last edited:
N-Gin said:
What forces act on which of them? In this case, it's easy to determine directions of their motion and calculate acceleration.



Some kind of force is required to change the motion of the system. Now, is there any way to obtain that force if Caitlin can't touch anything (just remember the definition of force)?

thanks :), I've calculated the acceleration which is 0.7ms-2 but i can still seem to find out how to find the tension :S
 
ahhhh don't worry delta explained it xD
 

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