Finding percentage and absolute uncertainties

[haha0p1]

Homework Statement

Find the percentage and absolute uncertainities in the young modulus if the uncertainty in the extension is ±1 mm.

Relevant Equations

Young modulus= Stress ÷ Strain

the answers to other parts of the question:

a, 2.0×10-⁷
b, 40 N
c, O.O5
d, 4×10⁹Pa
I Really don't understand how to solve the e part
I Know that Young modulus= (Force÷Area)÷(Extension÷Load)
kindly guide how to solve this question.

 

[BvU]

This is somewhat undetermined, because you have no information on the uncertainty of the other factors. My guess is that you are supposed to ignore them.

The simplest form (even simpler than this) says
relative error in product or quotient due to one of the factors is equal to relative error in that factor. So if ##f = A B## and A has an relative error of 0.2 and B has a relative error of negligible magnitude, then the relative error in ##f## is also 0.2

idem if ##f=A/B##.

If the error in ##B## can not be ignored (and is independent of the error in A) then the errors should be added in quadrature (see the link).

Does this help ?

##\ ##

 

[haruspex]

If you have not been taught the formulae @BvU quotes, an obvious way is to calculate the extreme values that the extension might really be and see what values those would give for the modulus.