Tension and Pulley Madness (Load weight)

In summary, the conversation discusses the use of tension in solving a physics problem involving a pulley system. The tension is constant across the cord, regardless of the number of pulleys. The correct answer is obtained by considering the tensions in both ropes connecting points A and B. The conversation also briefly touches on measuring tension in a catapult for a science project.
  • #1
jegues
1,097
3

Homework Statement


See figure.


Homework Equations


Sum of Fy = 0
Sum of Fx = 0
Tension is constant across the cord, regardless of the number of pulleys.

The Attempt at a Solution



My first thought after looking at the B A E connection to load P was that the hypotenuse of the 60 degree triangle must be 850 Newtons since tension is constant across the rope. Is there any flaws in my reasoning? (I can't seem to get the correct answer so there must be )



Also doesn't the tension in the cord ABCD depend on load P as well? The heaver P is, the greather the tension in the cord will have to be to keep the cord-pulley system from moving. I'm not sure what forces I'm suppose to use to obtain a tension across ABCD.



Any help is greatly appreciated.
 

Attachments

  • PulleyQ2.JPG
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  • #2
Hi jegues! :smile:
jegues said:
My first thought after looking at the B A E connection to load P was that the hypotenuse of the 60 degree triangle must be 850 Newtons since tension is constant across the rope. Is there any flaws in my reasoning? (I can't seem to get the correct answer so there must be )

There are two ropes between A and B.

Yes, 850 N is the tension in one rope.

But you still have a tension T in the other rope (along AB) (this is like that other thread of yours), and the same tension T along the rope BC.

Try again. :smile:
 
  • #3
Here's my attempt at a FBD, is this correct?

EDIT: AHA! Got it ;)

[tex]F_{x} :[/tex]

[tex] -(850 + T)cos60 + Tcos30 = 0 [/tex]

[tex] T = 1161.2N [/tex]

[tex] F_{y} :[/tex]

[tex](850 + T)sin60 + Tsin30 - P = 0[/tex]

[tex] P = 2322.24N [/tex]
 

Attachments

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Last edited:
  • #4
Excellent! :biggrin:
 
  • #5
how do you measure tension on a catapult because I'm doing a science project and i don't know how
 

1. How does tension affect the movement of a pulley system?

Tension is a force that is created by the pulling or stretching of an object. In a pulley system, tension is responsible for the movement of the load weight. As one end of the rope is pulled, tension is created, causing the pulley to move and lift the load weight. The tension in the rope remains constant throughout the system, allowing for a balanced and efficient transfer of force.

2. What factors affect the tension in a pulley system?

The tension in a pulley system is affected by the weight of the load, the number of pulleys in the system, the angle of the ropes, and the friction between the pulleys and the ropes. As the weight of the load increases, the tension in the rope also increases. More pulleys in the system can decrease the tension required to lift the load, but also increase the complexity of the system. A smaller angle between the ropes can also decrease tension, while friction can increase tension and reduce the efficiency of the system.

3. How can the load weight be calculated in a tension and pulley system?

The load weight in a tension and pulley system can be calculated by using the equation W = F x d, where W is the weight of the load, F is the tension force in the rope, and d is the distance the load is lifted. In a simple pulley system with one fixed pulley and one movable pulley, the weight of the load is equal to the tension in the rope. However, in more complex systems, the weight may need to be calculated using the equations for mechanical advantage and the number of pulleys in the system.

4. How does the number of pulleys affect the mechanical advantage in a tension and pulley system?

In a tension and pulley system, the mechanical advantage is the ratio of the output force (load weight) to the input force (tension in the rope). The number of pulleys in the system can affect the mechanical advantage, as more pulleys can decrease the input force required to lift a load. The mechanical advantage can be calculated using the equation MA = Load/Force, where MA is the mechanical advantage, Load is the weight of the load, and Force is the tension in the rope.

5. How can friction be reduced in a tension and pulley system?

Friction is an important factor to consider in a tension and pulley system, as it can decrease the efficiency of the system and increase the tension required to lift a load. One way to reduce friction is by using pulleys with bearings, which can reduce the contact area between the rope and the pulley, thus reducing friction. Additionally, lubricating the pulleys and using ropes with low friction coatings can also help to reduce friction in the system.

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