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Finding Magnification factor M for Frequency Ratio

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1) In the idealized model attached shown, m = 15 kg, k = 135 N/m, and the viscous damping ratio is 0.15. Assume that an external harmonic force F(t) = 15 cos 4 t acts on the system with F0=15 N and forcing frequency of 4 rad/s.
i) Find the magnification factor M for the frequency ratio r of 1.382.
ii) What is the amplitude of the response X?

For i ), which one is correct answer:
(a) 4
(b) 3
(c) 1

For ii ), which one is correct answer:
(a) 0.127
(b) 0.184
(c) 0.274

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Solution Summary

The solution finds the magnification factor M for frequency ratio. The amplitude of response X is determined.

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Assessment 2

Part A: Questions from the Drosophila melanogaster cross practical
1) Present the results of the Drosophila cross in a suitable format. Include your results and class results. (5)
2) Explain why a reciprocal cross might be carried out in an experiment like this. (4)
3) Research the genetic basis of vestigial wings in Drosophila melanogaster. (2)
4) Carry out a Chi square test of the class results based on what you found out about the genetics. Write a null hypothesis and show all of the steps clearly. State whether you should accept or reject the null hypothesis and state your conclusion. (10)

Part B: Questions from the polytene chromosomes practical
1) From your own observations in the practical, estimate the width of a polytene chromosome on your slide. (2)
2) What are polytene chromosomes and why do they arise? (10)
3) Research other species and tissues where polytene chromosomes have been found. (10)
4) Discuss the nature of "puffs" that occur in polytene chromosomes during development. (10)

Part C: Questions from the bacterial transformation practical
1) How much DNA in ng was added to each tube of bacteria? If 250pg of DNA was required, how many l would have been needed? Show your workings clearly. (6)
2) In week 1 of the practical, plasmids were introduced into competent bacteria and plated onto selective media. Present the results of your findings in an appropriate way and state which plasmid contains which resistance gene? (10)
3) Calculate the transformation efficiency for each of the transformations you performed. Show your workings clearly. (5)

Transformation efficiency (transformants/g) = Number of colonies on plate
g of DNA per transformation

5l of plasmid at 2ng/l were used per transformation.

4) What factors may affect transformation efficiency and why? (8)
5) Present results of the gel electrophoresis including labels for each lane. (6)
6) Give an estimate for the sizes of the plasmids in base pairs. (2)

Please do not exceed the word count of 1000 words. This word count does not include titles, tables, legends, figures or references.

A further 10 marks are available for references, presentation, clarity, depth of understanding and scientific content.

This assessment is due in Thursday 5th December 5pm.

Helen McRobie 2013

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