Unformatted text preview: controlled strain measurement on this material (i.e.,
systematically increase strain, measure resulting stress). If the material displays linearly
elastic behavior between a stain of 0 and 70%, and at a strain of 55% you measure a stress
of 40 MPa (40 x 106 N/m2), what is the Young’s modulus of the material? (10)
B. Now suppose you cut a strip of the material that is 100 cm in length and has a crosssectional area of 1 cm2, and you hang a 100 kg weight from it. Using your answer in A,
calculate the length of the material after you hang the weight. (10)
C. Now consider a completely different material, and suppose you conduct a creep test in
which you apply an instantaneous, constant stress (step stress) and measure the resulting
strain of the material. Sketch the strain response as a function of time for a (1) purely
viscous material, (2) purely elastic material, and (3) a Voigtmodel viscoelastic material
(spring and dashpot in parallel). In all cases, indicate the time at which the step stress was
applied, e.g. with an arrow. (10) a)
= b) 40
=
= 72.7 = 100 × 9.8 = 9.8 × 10
1
1
× 100
9.8 × 10
∆
∆
==
= 0.135 = =
72.7 × 10
100
∆ = 13.5
= + ∆ = 100
+ 13.5
= 113.5
c) = × 0.55 NAME:
NAME: SID: ε Viscous t ε Elastic t ε Voight t NAME:
NAME: SID:
SID: 4. Consider the following circuit: A. Suppose V = 1.000 V, R1 = 1.000 kOhm, R2 = 2.000 kOhm, R3 = 3.000 kOhm, and R(T) is
a thermistor that obeys the following equation: R (kOhm) = exp[100.0*(1/T – 1/300.0)]
where T is temperature in Kelvin. Derive an equation that describes the total current in
in
the circuit as a function of temperature. (15)
the
B. Using your answer in A, how much of a current change (in A) would be associated with
wer
an increase in body temperature from 37 C to 39 C? In order to avoid significant rounding
errors, carry 4 significant figures throughout your calculation. (10)
errors, NAME:
NAME: SID: NAME:
NAME: SID: 5. Suppose you are interested in measuring the concentration of a solution of the protein
lysozyme by spectrophotometry. If the intensity of...
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 Fall '09
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