What is the Tension in the String and the Mass of the Bar?

In summary, the bar is held horizontally and in equilibrium by an angled string that carries a 2kg mass at its free end and passes over a pulley. The tension in the string is calculated to be 19.6N, the weight of the mass. However, to show that the mass of the bar is approximately 3.5kg, further calculations are needed. The attempt at a solution involves resolving the tension vertically and using the pivot, but the resulting value does not match the desired mass. The use of work done also does not yield the expected result.
  • #1
Chewy0087
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Homework Statement


The bar is maintained horizontal & in equilibrium by an angled string which passes over a pulley and which carries a mass of 2kg at it's free end.

1) Calculate the Tension T in the String

2) Show that the mass of the bar is approximately 3.5kg

Homework Equations



-

The Attempt at a Solution



Included the picture there, it's a really easy question I guess but i think I'm missing something :confused:, or not understanding something very well...

for 1) I presume it's simply 19.6 N , the weight of the mass.

2) I'm a bit stuck here, what does it want you to use? If 19.6 in the tension in the string and you resolve it vertically I get 19.6cos 30 = 16.97 N which obviously doesn't work out to be 3.5kg, I think I'm missing something regarding the pivot, or maybe it's related to work done...

Any help would be great, it's just a stupid problem! :P

Edit: Using that work done thing - I got

(0.8 * 3.5) / cos (30) = 3.23 but still that's far off, so i don't think it can be that
 

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  • #2
Moments:wink:
 
  • #3
=P thanks
 

FAQ: What is the Tension in the String and the Mass of the Bar?

How does a pulley system work?

A pulley system uses a combination of wheels and ropes to distribute the weight of an object evenly over multiple ropes. As one rope is pulled, it rotates the wheel, which then pulls the other ropes in the system, making it easier to lift the object.

What is the mechanical advantage of a pulley?

The mechanical advantage of a pulley is the ratio of the output force to the input force. In a simple pulley system, the mechanical advantage is equal to the number of ropes supporting the weight. For example, a system with two ropes has a mechanical advantage of 2, meaning the input force is half the weight of the object being lifted.

How does adding more pulleys affect the mechanical advantage?

Adding more pulleys to a system increases the mechanical advantage. Each additional pulley reduces the amount of force needed to lift the object. For example, a system with four pulleys would have a mechanical advantage of 4, meaning the input force is only one-fourth of the weight of the object.

What is the difference between a fixed pulley and a movable pulley?

A fixed pulley is attached to a stable surface and only changes the direction of the force, while a movable pulley is attached to the object being lifted and reduces the amount of force needed to lift it. A combination of fixed and movable pulleys can create a compound pulley system, which combines the benefits of both types.

How does the weight of the bar affect the effort needed to lift it with a pulley system?

The weight of the bar affects the amount of effort needed to lift it with a pulley system. The heavier the bar, the more force is required to lift it. However, with a pulley system, the weight of the bar is distributed over multiple ropes, making it easier to lift compared to lifting the bar directly with only one rope.

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