Forces on a string applied perpendicular / tangent direction

[dislect]

Hello guys,

I've had the following discussion at work:

We are currently using a suture with a nylon thread on a tissue, when the thread of the suture is tightened in a force equal to if we've put a 500 gram weight on both ends of the suture line (meaning both end are tied together to the weight).
The assumption is that in this mode, the tissue will fail with a load higher than that.

We were wondering, if the force was applied perpendicularly (direction of the screen) would the max wight change from 500 gram to another value?

Would love a direction to some equations to rationalize my first instinct of saying "No!" :-)

Thanks!

 

[Simon Bridge]

It does not matter which direction the force is applied - a 500g-force is a 500g-force.
The effect this has on the suture/tissue may be different at different angles.

Note: two ends tied and attached to 500g - each thread has to support 250g + whatever lateral forces are produced by pulling on the tissue. That's something like 250g tension in the thread.

Your diagram has a total of 500g-force applied at three places on the thread ... So each attachment point is supporting 500/3 g-force ... and each is basically the same as two ends, so the tension in the thread is 500/6 g-force.

S the answer kinda depends on the specifics of the question you want to ask.

 

[dislect]

Hi, thanks.
Yes I recon it depends on things like the length of the suture, its width, angles and so on.
But assuming both are identical for the two cases, the tension of the suture would still be 500/6 even if we apply it in at the direction of the screen instead of "pulling it" like in pic 1 (?)

 

[Simon Bridge]

In one pic the weight is applied to only one location in the loop - in the other pic the force is applied to three locations at the same time - if I read that right. That's what makes the biggest difference since it's the same total force.

 

[PJC01]

I would say that the forces on a string applied perpendicular or tangent to its direction depend on the properties of the string and the object it is attached to. In the case of the suture with a nylon thread, the force applied perpendicular to the string would likely cause the tissue to fail at a lower weight compared to when the force is applied tangent to the string. This is because the perpendicular force would cause the string to stretch and potentially break, whereas the tangent force would distribute the load more evenly along the string.

To rationalize this, we can look at the equations for tension and stress. Tension is the force applied to a string, and stress is the resulting force per unit area on the object. When the force is applied perpendicular to the string, the tension will be higher and therefore the stress on the tissue will be higher as well. This can lead to failure at a lower weight compared to when the force is applied tangent to the string.

Additionally, the angle at which the force is applied can also affect the maximum weight that the tissue can withstand. If the force is applied at an angle between perpendicular and tangent, the tension and stress will be somewhere in between the two cases discussed above.

In conclusion, the direction of the force applied to a string can greatly affect the maximum weight that can be withstood by the tissue it is attached to. It is important to consider the properties of the string and the object when determining the effects of forces applied in different directions. I would suggest conducting further experiments or simulations to better understand the specific values and conditions in this scenario.