Calculating the Young's Modulus of Rubber - Calculation Check

[RajdeepSingh7]

Homework Statement

Dear Yahoo Answers,
Can someone please help me with this as it's driving me crazy!
We had to complete an experiment where had to calculate the Young’s modulus of Rubber,
by doing an experiment.
So we used a rubber band and various weights to calculate the values, to hence calculate the Young's Constant.

Homework Equations

My values are as follows:

Force = 0.4 kg = 3.92 Newtons
Orginal Length = 50mm
Change in Length = 184.33mm
( Therefore Final Length = 234.33mm)
and Area = 2.5 mm^2

The Attempt at a Solution

Do these values look approximately correct,
and does the final Modulus value of 425 324.147 N/m^-2
look alright for that of rubber?

The problem of that would be that it's actually too small for the actual range for the Modulus,
between 0.1 and 0.01 * 10^9 N/m^2.

Clearing this up for me would be greatly appreciated.
Any help and/or contribution will be great appreciated too.

Thanks.

 

[haruspex]

Are you sure you measured the area correctly? Remember it will narrow as it is stretched.

 

[Delta2]

@haruspex I 've noticed you reply to this old threads like the OP is going to hear you and you going to have a dialogue with him but this 99.99% isn't going to happen. The point of replying this unanswered threads is so that future google readers will find them useful and PF will get better google score.
I suggest if you going to reply to these threads to give strong hints towards their solution or even write the full solution. Or give some guidelines so that someone that knows the basics of theory will be able to solve the problem if he follows your guidelines.

 

[haruspex]

@haruspex I 've noticed you reply to this old threads like the OP is going to hear you and you going to have a dialogue with him but this 99.99% isn't going to happen. The point of replying this unanswered threads is so that future google readers will find them useful and PF will get better google score.
I suggest if you going to reply to these threads to give strong hints towards their solution or even write the full solution. Or give some guidelines so that someone that knows the basics of theory will be able to solve the problem if he follows your guidelines.

Yes, I am quite aware the original OP is long gone, but it still seems right just to give the hint/correction I would have given at the time. Remember that one reason for this exercise is to show what help can be expected from the forum.

Another student coming in with the same question should not be presented with a full solution, and may well gain from the hint offered. If their issue is different, they can post to the thread.

 

[Delta2]

Well ok that's another way to deal with this situation...

 

[kuruman]

My decision on how to respond to these was to ignore the age of the original post and proceed as usual. We have our guidelines for providing help and we believe in them for good reason. In my opinion, deviating from them will blur the line between PF and the "for hire" problem-solving sites.