Mechanics I ME102

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The objective of this session is to introduce the subject of software engineering. When you have read this session you will understand what software engineering is and why it is important, know the answers to key questions which provide an introduction to software engineering, understand ethical and professional issues which are important for software engineers.

Introduction

Virtually all countries now depend on complex computer-based systems. More and more products incorporate computers and controlling software in some form. The software in these systems represents a large and increasing proportion of the total system costs. Therefore, producing software in a cost-effective way is essential for the functioning of national and international economies.

Software engineering is an engineering discipline whose goal is the cost-effective development of software systems. Software is abstract and intangible. It is not constrained by materials, governed by physical laws or by manufacturing processes. In some ways, this simplifies software engineering as there are no physical limitations on the potential of software. In other ways, however, this lack of natural constraints means that software can easily become extremely complex and hence very difficult to understand.

Software engineering is still a relatively young discipline. The notion of ‘software engineering’ was first proposed in 1968 at a conference held to discuss what was then called the ‘software crisis’. This software crisis resulted directly from the introduction of powerful, third generation computer hardware. Their power made hitherto unrealisable computer applications a feasible proposition. The resulting software was orders of magnitude larger and more complex than previous software systems.

Early experience in building these systems showed that an informal approach to software development was not good enough. Major projects were sometimes years late. They cost much more than originally predicted, were unreliable, difficult to maintain and performed poorly. Software development was in crisis. Hardware costs were tumbling whilst software costs were rising rapidly. New techniques and methods were needed to control the complexity inherent in large software systems.

These techniques have become part of software engineering and are now widely although not universally used. However, there are still problems in producing complex software which meets user expectations, is delivered on time and to budget. Many software projects still have problems and this has led to some commentators (Pressman, 1997) suggesting that software engineering is in a state of chronic affliction.

As our ability to produce software has increased so too has the complexity of the software systems required. New technologies resulting from the convergence of computers and communication systems place new demands on software engineers. For this reason and because many companies do not apply software engineering techniques effectively, we still have problems. Things are not as bad as the doomsayers suggest but there is clearly room for improvement.


Mechanics studies how forces affect bodies in motionhow, for example, a bullet is fired from a gun or a top is set in motion by the flick of a wrist. As an engineer, you will find mechanics of vital importance to any field you choose to pursue. Whether you are designing a bridge or implementing an electrical power unit for an elevator, you will need to know how to determine which forces can be applied to a body without causing it to break, what happens when bodies collide, how an object moves when different forces are applied to it, and so on. This course will introduce you to the core concepts of mechanics that will enable you to answer these questions as you strive to design, test, and manufacture safe and reliable products.

While most universities split introductory mechanics into two courses, with one devoted to statics and the other to solids, this course will introduce you to both areas. You will begin by learning about staticsobjects that are not accelerating (in other words, objects that are either at rest or moving at a constant speed). In this course, you will be able to visualize and understand how rigid bodies react to applied forces without having to worry about how the rate of acceleration or deceleration will impact the body. (These considerations are for later engineering courses that study dynamics.) You will also learn how to solve force and moment problems by drawing free body diagrams and applying equilibrium equations. You will learn to compute moments and resultants of force systems and study internal forces exerted on members. You will analyze trusses, machines, and frames, as well as study the effects of friction on belts and wedges.

Quiz PDF eBook: 
Mechanics I ME102
Download Mechanics I MCQ Quiz PDF eBook
40 Pages
2014
English US
Educational Materials



Sample Questions from the Mechanics I ME102 Quiz

Question: How do beams differ from truss elements?

Choices:

Beams are wider and stiffer than truss elements.

Beams are solid, but truss elements usually have void spaces for weight concerns.

Beams have more complex cross sections than truss elements.

Truss elements are usually pin connected and carry only axial loads, but beams may have connections like welds that impart transverse loads.

Truss elements are subject to bending forces, but beams are not.

Question: Why did full-scale engineering-material specimens fracture at lower loads than expected in early metal airplanes (see specifically the Comet 1)? I. The effects of cyclic fatigue were not appreciated for airplane pressurization/depressurization. II. The effects of stress concentration at the corners of square windows were not appreciated. III. The effects of defect presence and growth were not appreciated for large structures

Choices:

I only

Both II and III

I, II, and III

Both II and III

Both I and III

Question: Which of the following represents the area moment of inertia of a thin, rectangular body about an axis through the center of the body and parallel to the long dimension of the rectangle? The long dimension of the rectangle is 10 cm and the short dimension is 5 cm.

Choices:

1.0 x 10 [sup] -6 [/sup] m [sup] 4 [/sup]

1.0 x 10 [sup] 2 [/sup] m [sup] 4 [/sup]

1.0 x 10 [sup] -4 [/sup] m [sup] 4 [/sup]

1.0 x 10 [sup] -6 [/sup] m [sup] 2 [/sup]

2.0 x 10 [sup] -5 [/sup] m [sup] 4 [/sup]

Question: Which of the following is a correct definition of Poisson's ratio?

Choices:

It is the ratio of transverse strain to normal strain, resulting from normal stress.

It is the ratio of specimen volume upon compression with a known stress to that without compression.

It is the ratio of the rebound length of a material specimen after temporary extension to its initial length.

It is the ratio of shear stress to normal stress.

It is the ratio of shear strain to normal strain.

Question: Which of the following statements best describes finite element analysis?

Choices:

It is a numerical method for inverting a matrix or tensor.

It is a computational technique for solving for stress as a function of strain.

It is a modeling technique limited to a finite number of engineering pieces.

It is a useful numerical method limited to linear differential equations.

It is a numerical method for approximating solutions to differential and other equations.

Question: How does creep differ from fatigue?

Choices:

Creep refers to slow deformation resulting in change in macroscopic shape; fatigue refers to the weakening of material over time caused by repeated use or loading.

They do not differ.

Creep refers to the overall weakening of a material through pressure; fatigue refers to the weakening that occurs at susceptible stress points.

Creep is temperature dependent; fatigue is not.

Creep is more significant for very large pieces than fatigue; fatigue is more important for small pieces that fail as a result of small-crack propagation.

Question: Which of the following assumptions are necessary in order for the beam deflection equation to be well represented by d[sup]4[/sup]w(x)/dx[sup]4[/sup] EI = q(x)? I. Constant E II. Continuously distributed loads only III. Constant I

Choices:

I only

II only

Both II and III

Both I and II

I, II, and III

Question: For a cantilevered beam with a downward load L at the free end, which of the following statements is true? I. The shearing force is constant over the length of the beam. II. The magnitude of the bending moment increases linearly from the fixed end to the free end. III. The magnitude of the shearing force increases linearly from the free end to the fixed end. IV. The beam bends so that it is concave up.

Choices:

II, III, and IV

Both III and IV

Both II and III

I only

Both I and II

Question: Which number of cycles conventionally lies between low-cycle and high-cycle fatigue?

Choices:

10

1000

200,000

20,000,000

1,000,000,000

Question: Which of the following best describes the process of fatigue for engineering materials?

Choices:

Fatigue is material corrosion that prevents further use.

Fatigue is the failure or weakening of material caused by repeated or continued stress or loading

Fatigue is the natural aging of material that leads to failure.

Fatigue is the weakening of engineering materials caused by thermal cycling and the resulting molecular rearrangements that occur.

Fatigue is the temporary weakening of materials resulting from continued use; materials may recover strength if random molecular rearrangements are allowed to occur during a period of disuse.

Question: Which of the following are well-established experimental tools for determining localized strains in engineering pieces? I. Localized electrical resistance measurements in strain gauges II. Optical methods based on photoelasticity III. Ultrasonic displacement mapping IV. X-ray or computed tomography

Choices:

II only

Both II and III

Both I and IV

Both I and II

I, II, III, and IV

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Source:  Stephanie Redfern, Ranjeet (Ron) Agarwala, and Dr. Steve Gibbs. Mechanics I. The Saylor Academy 2014, http://www.saylor.org/courses/me102/
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