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Semester 2 Examinations 2011/ 2012
Exam Code(s) 2BG Exam(s) 2 nd^ Biomedical Engineering
Module Code(s) ME Module(s) Introduction to Biomedical Engineering
Paper No. 1 Repeat Paper
External Examiner(s) Internal Examiner(s) Professor Peter McHugh Dr. Laoise McNamara Dr. Patrick McGarry
Instructions: (^) This paper contains 4 questions Answer 3 questions All questions will be marked equally
Duration 2 hours
No. of Pages 5 Department(s) Mechanical & Biomedical Engineering Course Co-ordinator(s) Dr. Laoise McNamara
Requirements: Statistical/ Log Tables
Release to Library: Yes
Question 1:
(a) Identify the main forces involved in successful swimming performance. In your answer identify and describe: (i) Forces that propel the swimmer. (ii) Forces that resist movement of the swimmer through the water. [6]
(b) A swimmer is 82% submerged while floating in the pool. Estimate the buoyant force exerted on the swimmer if the volume of the person is 0.072 m^3 and the specific weight of water is 9.806 kN/m^3. If the swimmer inhales and increases their volume by 5%, how does this affect the buoyant force on the swimmer? [4]
(c) During a swimming race a swimmer’s hand travels at a speed (v) of 2.5 m/s, see Figure Q1. The pressure acting on the back of the hand is 1.5 x 10^5 Pa and the pressure acting on the front of his hand is 0.25 x 10 5 Pa. The surface area of the hand is 8.1 x 10-3^ m^2 , the coefficient of drag of the hand is 0.56 and the density of water is 1g/cm^3.
(i) Estimate the drag force generated by the swimmers hand. [3] (ii) Estimate the coefficient of lift. [5]
(d) Calculate the total propulsion generated by the hand. [2]
Figure Q
Question 3
Figure Q3(a) Figure Q3(b)
Figure Q3(a) shows a schematic of a person of weight W balancing on one leg. In addition to the reaction force at the foot due to body weight W , the self-weight of the leg, W 1 , acts at point B (the
centre of mass of the leg). The hip abductor muscles act at an angle to the horizontal and exert a
force FM. Figure Q3(b) shows an idealized free-body diagram of the leg (excluding force vectors).
is the angle between the leg and the horizontal. is the angle between the femoral neck and the
horizontal. O is the hip joint, B is the centre of mass of the leg, and C is the foot.
(a) Derive expressions for the hip abductor muscle force FM and the hip joint reaction force (at O). [15]
(b) For a person is of height h and weight W , the following parameters can be assumed:
a =|OA|=0.05 h ; b =|AB|=0.2 h ; c =|AC|=0.52 h ; =45o^ ; =80o^ ; =70 o^ ; W 1 =0.17 W. What is the
magnitude of the hip joint reaction force (expressed as a function of W )? [5]
Question 4
(a) Derive the general equation for a Maxwell viscoelastic model (spring and dash-pot in series). [3]
(b) Derive the response of a Maxwell model to a stress-relaxation test. [4]
(c) Derive the general equation for a Kelvin-Voigt viscoelastic model (spring and dash-pot in parallel). [3]
(d) Derive the response of a Kelvin-Voigt model to a creep test. [4]
(f) Sketch the stress relaxation behavior for a tendon. Also sketch the stress relaxation behavior predicted by a Maxwell viscoelastic model. Explain briefly why the Maxwell model is not suitable for modelling tendons. [6]
