- #1
aqdus
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what will be tension on string pulled by equal but opposite forces?
What will be tension on string pulled by equal forces?
- Thread starter aqdus
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- Forces String Tension Tension force
In summary, when equal but opposite forces are applied to a string, the net force on the string is zero but this does not mean that the tension on the string is also zero. This is because the two forces are not an action-reaction pair and correspond to different interactions. Even with a net force of zero, tensions can still develop in the string, causing it to stretch. This is often seen in problems with massless strings, where the tension is assumed to be constant and equal to one of the forces applied.
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aqdus
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but in both cases there will be two but opposite forces on string so net force will be zero on string why the tension is not zero ?
- #4
staralfur
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When you draw a free body diagram be careful not draw both forces in a action-reaction pair. In a action-reaction pair the forces don't act on the same body. If you and I both pull the string with equal but opposite forces, I am the body which you apply force to and you are the body I apply force to. The sketch I made wasn't a FBD as it contained both forces.
- #5
nasu
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The two forces acting at the two ends of the string are not an action-reaction pair. They correspond to two different interactions.
At one end (let's say where you pull by hand) there is the interaction hand-string. You pull with F1, the string pulls with -F1.
At the other end you have interaction between the string and wall and again you have F2 on the string and -F2 on the wall.
If the center of mass of the string does not accelerate, you will have F1=F2 (in magnitude) and the net force is zero. This does not prevent tensions developing in the string.
The fact that the net force is zero just tell you that the acceleration is zero. But they don't have to be equal.
Now, usually the string is assumed massless in elementary problems so even when we have acceleration the two forces are taken as equal. And the tension along the string is assumed to be constant and equal to either one of these forces.
So, to go back to the point, you can and many times do, create tension in a body by applying equal forces at different points of the body.
At one end (let's say where you pull by hand) there is the interaction hand-string. You pull with F1, the string pulls with -F1.
At the other end you have interaction between the string and wall and again you have F2 on the string and -F2 on the wall.
If the center of mass of the string does not accelerate, you will have F1=F2 (in magnitude) and the net force is zero. This does not prevent tensions developing in the string.
The fact that the net force is zero just tell you that the acceleration is zero. But they don't have to be equal.
Now, usually the string is assumed massless in elementary problems so even when we have acceleration the two forces are taken as equal. And the tension along the string is assumed to be constant and equal to either one of these forces.
So, to go back to the point, you can and many times do, create tension in a body by applying equal forces at different points of the body.
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aqdus said:
Do you really expect an elastic band not to stretch if you pull it from both ends? Its centre of mass won't move because there is no nett force, but it's certainly going to stretch.
Related to What will be tension on string pulled by equal forces?
1. What is tension?
Tension is a force that is exerted on an object when it is pulled, stretched, or twisted. It is a measure of the internal forces that are acting on an object to keep it in equilibrium.
2. How is tension calculated?
Tension is calculated as the product of the force applied and the distance over which it is applied. In the case of equal forces pulling on a string, the tension can be calculated by dividing the total force by the number of strings.
3. What factors affect tension on a string?
The tension on a string is affected by the magnitude of the applied force, the length of the string, and the material properties of the string such as elasticity and density.
4. Can tension on a string be greater than the applied force?
No, tension on a string cannot be greater than the applied force. However, if the string is attached to an object, the object may experience a greater force due to the tension on the string.
5. How does the angle of the string affect tension?
The angle of the string affects the tension by changing the direction of the applied force. When the angle is increased, the tension on the string decreases, and vice versa. This is because the component of the force acting perpendicular to the string decreases with increasing angle.
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