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Re: How to measure stress/tension on a rope?

put finger to keyboard and composed:

Just to be pedantic, that's the oscillation period, not frequency.

And "proportional" implies a linear relationship, not sqrt.

And the formula strictly only holds for a "simple" pendulum, ie one

where the oscillation angles are small.

See http://hyperphysics.phy-astr.gsu.edu/hbase/pendl.html

As for your interpretation of Hooke's Law, how long is a string when

no force is applied to it? ;-)

Hint #1: F = k.dL, not F = k.L.

See http://www.ac.wwu.edu/~vawter/PhysicsNet/Topics/SHM/HookesLaw.html

Hint #2: Would a 100kg mass swing with 10 times the period of a 1kg

mass, if released at the same angle?

-- Franc Zabkar

Please remove one 'i' from my address when replying by email.

Just to be pedantic, that's the oscillation period, not frequency.

And "proportional" implies a linear relationship, not sqrt.

And the formula strictly only holds for a "simple" pendulum, ie one

where the oscillation angles are small.

See http://hyperphysics.phy-astr.gsu.edu/hbase/pendl.html

As for your interpretation of Hooke's Law, how long is a string when

no force is applied to it? ;-)

Hint #1: F = k.dL, not F = k.L.

See http://www.ac.wwu.edu/~vawter/PhysicsNet/Topics/SHM/HookesLaw.html

Hint #2: Would a 100kg mass swing with 10 times the period of a 1kg

mass, if released at the same angle?

-- Franc Zabkar

Please remove one 'i' from my address when replying by email.

Re: How to measure stress/tension on a rope?

Pendulum, yes.

But length only, not weight. Therefore, probably no help here.

Perhaps if you knew the length and weight of the string, you

could calculate the center of mass by the period of the swing,

then from that the mass of the object.

But my last Physics class was about 30 years ago...

Rufus

Re: How to measure stress/tension on a rope?

I dont know the maths (too long ago when I did this sort of thing) but surely

applying a force to the object that moves it a distance by a transducer then you

can calculate the weight of the object - eg m=force x distance or something -

then by measuring the period of the swing you can calculate the length of the

string.rope and by using a lazer 'device' measure the diam of the rope/wire etc

you can calculate it own weight (or close to it) - then the stress etc becomes

the sum of the object plus the weight of the string

Or am I just rambling?

David - who loved physics but was hopeless at maths

Jim Stewart wrote:

applying a force to the object that moves it a distance by a transducer then you

can calculate the weight of the object - eg m=force x distance or something -

then by measuring the period of the swing you can calculate the length of the

string.rope and by using a lazer 'device' measure the diam of the rope/wire etc

you can calculate it own weight (or close to it) - then the stress etc becomes

the sum of the object plus the weight of the string

Or am I just rambling?

David - who loved physics but was hopeless at maths

Jim Stewart wrote:

Re: How to measure stress/tension on a rope?

a

string?

Piece of cake. Build a simulator, that is, an exact replica of the size or

wire or string, the length, and fix one end of the string to an anchor, and

the other end over a pulley with a weight on it. Now take a spring scale

such as those used by fishermen and hook your stretched string in the

middle. Have a piece of paper behind the line and mark the paper along the

straight line. Now hook onto the middle of the string and apply pressure.

Measure the distance in inches or centimeters, and write down the pull in

pounds or grams at different distances. Now change the weight on the string

and repeat the experiment. With this information in hand you can do a simple

proportional formula extrapolation for the unknown in your actual case.

Let us know what happens since this seems to be a very interesting thread.

Wayne

www.pueblaprotocol.com

Re: How to measure stress/tension on a rope?

The tighter the rope the higher resonant frequency becomes like stretching

an elastic band. It would require something to give it a twang and a microhone

to pick up the resulting ringing.

-----------------------------------------------------------------------

Ashley Clarke

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