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Does the tension in an inextensible string depend on its material?

we know how tension does not go beyond a certain limit and always remains constant in an inextensible string. But does the VALUE of that tension depend on the material the string is made from under the SAME force? For e.g. if a string made from copper has a tension of 20N when a 30N force is applied on it, will the same nylon string have a 10N tension under this 30N force or something like that?(thus an object pulled by nylon will have a smaller acceleration??). Lets say both strings are inextensible.

Reply 1

Joinedup

Original post by Tucosalamanca01

No - but pay attention to whether you're being asked a mechanics type question with inextensible strings and inflexible beams OR a materials type question where they give you the Youngs modulus of a material.

tbh I've never seen a A level question that's said 'an inextensible string made of nylon' - can you provide an example of the type of question that's confusing you?

Reply 2

Asuna Yuuki

What.

If a constant 30N force is applied to ANY inextensible string, there will be 30N of tension in the string. Unless you want it to start being extensible, I guess.

Inextensible is generally applied to models so shouldn't really have much relevance when it comes to materials.

Reply 3

anosmianAcrimony

In real life, using real materials, there's no such thing as an inextensible string. The inextensible strings you use in mechanics are basically made out of witchcraft.

Reply 4

hug-burs

Of course they'll have the same force - if they're both in extensible no energy is lost! Eg. No energy is lost as heat, no energy is stored as elastic potential. All of the force applied to the string is also applied to the object if in extensible, wether it be made of copper, nylon, rubber, flesh, a pillow - they're all rigid in this situation.

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(edited 7 years ago)

Reply 5

Tucosalamanca01

Original post by Joinedup

Thanks I got it now! Value of tension does not depend on the material, but only on the force applied, right? On another note, isnt it true that a weaker string will break before the one made up of a stronger material given that the same high tension force is acting on both the strings?
As for your example I actually made this question up.

Reply 6

Tucosalamanca01

Original post by Asuna Yuuki

Thanks for your answer, but I think you're wrong over there.
By your logic, if a car exerts a 30N force on a string/towbar connected to a trailer, then the tension will be 30N. But doesnt this mean there will be no resultant force and the car will NEVER move.
Hence I dont think the tension always has to equal the force applied. A stringed object can always move.

Reply 7

Tucosalamanca01

Original post by hug-burs

Hahahaa pillow XD thanks for the help man I got it now.
On another note though, say under the same high tension force, wont a string made up of pillow break before the one made of copper( coz pillows are weaker?)

Reply 8

Asuna Yuuki

Original post by Tucosalamanca01

No. The tension in an inextensible string will always be equal to the pulling force applied to it.

The resultant force in your scenario is the reaction to the driving force from the road, which has nothing to do with the object attached by the string. The trailer is not accelerating relative to the car.

Reply 9

Tucosalamanca01

Original post by anosmianAcrimony

In real life, using real materials, there's no such thing as an inextensible string. The inextensible strings you use in mechanics are basically made out of witchcraft.