Question 1

The second moment of area is?

Accepted Answer

The second moment of area is sometimes known as the 'area moment of inertia', is a property of a cross section that can be used to predict the resistance to bending and deflection about the neutral axis, and is dependent upon the cross-sectional shape of the structure.

Question 2

The polar second moment of area is?

Accepted Answer

The polar second moment of area is a measure of a cross-section's ability to resist torsion (twisting) about its axis, which is directly related to the resistance to torsional load about the long axis of a cylinder.

Question 3

Strain (ε) is defined as?

Accepted Answer

The answer of Strain (ε) is defined as?
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Question 4

The relationship between stress and strain can be visualised by plotting stress as a function of strain (Figure 1.7 in the text) The stress-strain (σ-ε) ratio, the ratio of the stress to the strain in that region for a particular load type, provides a numerical value of what?

Accepted Answer

The stress-strain ratio provides a numerical value of the elastic modulus, which is a measure of the stiffness of the material. Therefore, the correct choice is C - the elastic modulus. A is incorrect because compliance modulus is the reciprocal of elastic modulus. B is incorrect because shear modulus is a measure of the material's resistance to deformation by shear stress. D is incorrect because compressive modulus is not a commonly used term in material science, and it is not related to stress-strain behavior.

Question 5

Linear materials operate according to Hooke's Law, which means that ____________.

Accepted Answer

Linear materials, according to Hooke's Law, exhibit a linear relationship between stress and strain where the material returns to its original shape once the load is removed, indicating no permanent deformation and implying no energy loss due to the load.

Question 6

Biological materials are viscoelastic, what does this mean?

Accepted Answer

Viscoelasticity refers to a material's ability to exhibit both elastic (recoverable) and viscous (non-recoverable) behavior under load. In the case of biological materials, this means that their mechanical response is not entirely linear (option A) and is also affected by the tissue's fluid component (option C). Therefore, both option A and C are correct and the answer is D. Option B, which describes an entirely elastic behavior, is incorrect.

Question 7

The term 'hysteresis' refers to?

Accepted Answer

Hysteresis refers to all of the above - the differences in the load-deflection curve for loading and unloading, the energy loss proportional to the gray shaded area under the stress-strain curve, and the "permanent set" that remains when a material has entered the region of plastic deformation.

Question 8

Strain energy is stored in any deformed material during deformation. Which of the following statements regarding strain energy are true?

Accepted Answer

Choice A is true, as elastic strain energy is the energy stored in a material when it is deformed elastically, meaning that it can be recovered when the material returns to its original shape. In contrast, plastic strain energy is the energy stored in a material when it is deformed plastically, meaning that it cannot be fully recovered and is lost.

Choice C is also true, as the area under the stress-strain curve up to a given point is proportional to the strain energy stored in the material up to that point. This is known as the strain energy density and is often used in materials science and engineering to quantify the amount of strain energy stored in a material.

Choice D is also true, as strain energy can be stored in many different types of deformed materials, such as a trampoline bed, vaulting pole, shoe sole, protective equipment, or compressed ball. In all of these cases, the energy is stored in the material as a result of its deformation, and can be released or used when the material returns to its original shape or is subjected to an external force.

Question 9

One of the major differences between biological materials and non-biological materials is how load affects them over time. What is this time dependent behaviour is called?

Accepted Answer

The time dependent behaviour of materials is called viscoelasticity, which refers to the ability of a material to exhibit both elastic and viscous properties. This means that the material can withstand stress initially like an elastic solid, but will eventually deform under sustained loading like a viscous fluid. Hook's Law is a concept that relates the amount of deformation to the amount of stress applied, but it does not specifically address time dependence. Hysteresis describes the phenomenon where the response of a material depends on its history of loading and unloading. Resilience refers to the ability of a material to absorb energy and deform elastically without experiencing permanent deformation or damage.

Question 10

In a biological material the measured strain is a function of stress, time and temperature. When a material deforms as a function of time under a constant load, we call this phenomenon _______.

Accepted Answer

The phenomenon described is creep, which is the time-dependent deformation under a constant load. Stress-relaxation refers to the decrease in stress over time for a constant strain, viscoelastic refers to materials that display both elastic and viscous behavior, and hysteresis refers to the lag in response when stress is applied and then removed.

Question 11

In a biological material the measured strain is a function of stress, time and temperature. When a material undergoing a constant strain will begin to relax, we call this phenomenon

Accepted Answer

When a material undergoing a constant strain begins to relax, this phenomenon is called stress-relaxation. This is because the stress decreases over time while the strain remains constant. Viscoelasticity refers to the property of materials that exhibit both viscous (flow under stress) and elastic (recover their shape after stress) behavior. Creep is the gradual deformation of a material under stress over time. Hysteresis refers to the dependence of a system's output not only on its current input but also on its history of past inputs.

Question 12

The mechanical properties of most biological material are directionally dependent which means their mechanical properties depend on the direction in which they are loaded. What is the mechanical term that used to describe this Phenomenon?

Accepted Answer

The mechanical term used to describe this phenomenon is anisotropy which means that the material exhibits different mechanical properties in different directions. Isotropy (choice A) refers to materials with the same mechanical properties in all directions. Homogeneity (choice C) refers to materials with the same composition throughout, while non-homogeneous (choice D) refers to materials with varying composition or structure throughout.

Question 13

Cortical bone is a non-homogeneous, anisotropic, viscoelastic, brittle material which is weakest when loaded in __________.

Accepted Answer

Cortical bone is weakest when loaded in tension, as it is a brittle material and more likely to fracture under tensile stress.

Question 14

The overall structure of long bones gives an optimal strength-to-weight ratio. How is this achieved?

Accepted Answer

The cancellous component, with its spongy structure, helps absorb impact and prevent the denser cortical component from cracking, while the cortical component provides strength and rigidity, preventing the cancellous component from yielding.

Question 15

Bone is a viscoelastic material; thus, rate of loading is important to its biomechanical behaviour. What happens to bone when loaded at higher rates?

Accepted Answer

When bone is loaded at higher rates, it exhibits a greater elastic modulus, meaning it becomes stiffer and can sustain more load before deforming. This is due to its viscoelastic properties, where the material's response to stress is time-dependent.

Question 16

Which of the following statements regarding the biomechanical properties of cartilage is correct?

Accepted Answer

After the load is removed, cartilage returns to its initial elasticity within a relatively short time providing that the load was of short enough duration and low enough magnitude. Option A is incorrect because deformation of cartilage helps to increase joint range of motion and decrease joint contact area. Option B is incorrect because the elastic modulus of cartilage in compression increases with increasing depth from the cartilage surface. Option C is incorrect because the compressive modulus of cartilage increases with load as the cartilage is compressed and the chondrocytes resist the load.

Question 17

Total tension in a muscle is dependent on the tension length characteristics of both the active and passive components of muscle. Which of the following statements regarding active tension in a muscle are correct?

Accepted Answer

The answer of Total tension in a muscle is dependent...

Question 18

What are the three fundamental conditions of an effective stretch-shorten cycle (in order)?

Accepted Answer

The three fundamental conditions of an effective stretch-shorten cycle are: first, a well timed preactivation of the muscles before the eccentric phase to prepare the muscle for the upcoming contraction; second, a short and fast eccentric phase to create stored elastic energy in the muscle; third, an immediate transition between eccentric and concentric phases to take advantage of the stored energy and increase the force of the subsequent concentric contraction. Option B lists the conditions in the correct order.

Question 19

Because of their non-linear tensile properties (Figure 1.18), ligaments offer early and increasing resistance to tensile loading over a narrow range of joint motion. Which of the following statements most appropriately describes the practical implications of this phenomenon?

Accepted Answer

All the statements correctly describe the practical implications of the non-linear tensile properties of ligaments. A) explains how ligaments become stiffer at higher forces, B) describes the process of collagen fiber recruitment and joint stabilization, and C) differentiates between the stress-strain curve regions for daily and strenuous activities.

Question 20

Which of the following statements regarding the mechanical properties of tendon are false?

Accepted Answer

This statement is false because due to its viscoelastic behaviour, tendon is able to store and release energy efficiently, even when subject to large forces.

Quiz 1: Biomechanics of Sports Injury