Theoretical and Applied Mechanics 2020/T&AM 2020

Three lectures and one recitation each week. 4 two-hour labs with reports.

ENGRD 202 is required for all Mechanical, Civil, Material's Science and Biological Engineering students.

**Official description: **Covers principles of statics, force systems, and equilibrium;
frames; mechanics of deformable solids, stress, strain, statically indeterminate
problems; mechanical properties of engineering materials; axial force, shearing
force, bending moment, thermal stress, stretching; bending and torsion of bars.
Laboratory experiments demonstrate basic principles of solid mechanics.

Except for students who have some taste from the optional freshman introduction to engineering courses ENGRD 1160 or ENGRD 1170 (introductions to Civil and to Mechanical Engineering), students' first course that directly addresses engineering applications is ENGRD 2020. Engineering 2020 teaches concepts, skills, methods and formulas that are used every day by thousands of engineers. At the end of this course a student understands much of how structures hold together and fall apart, and can do useful engineering calculations to predict whether or not a structure will fail.

ENGRD 2020 combines into one course two traditional courses: one in Statics and one in Strength of Solids. Both of these are of a general type that has been taught for over 100 years at all engineering schools. These two courses were combined into one at Cornell several decades ago. Presumably it was thought that with Physics brought into the common curriculum that the number of engineering mechanics courses could be reduced. But for notational changes (vectors), and examples being drawn from modern looking machines, structures and from biomechanics, the equations, problems and examples used in ENGRD 2020 now are essentially the same as those used in 1880.

Because the material covered is universally agreed to be so basic to the engineering of physical objects, the course coverage has co-evolved nationally with the available textbooks. The course is generally taught from this selection of books, or books closely related to these in content:

- Engineering Statics texts by Beer&Johnston, Meriam&Kraige, Hibbeler, etc. and
- Strength of Solids texts by Beer&Johnston, Meriam&Kraige, Hibbeler, Geer, etc.

Because this course is so central to so many, the department keeps a close eye on its content and on the satisfation of its customers (the students and the later teachers of these students). Now and then, about once a year since 2001, a liason committee consisting of faculty from Mechanical Engineering, Civil Engineering, Materials Science, and Theoretical and Applied Mechanics meets to discuss the course.

The content of the course is:

Statics

- Vectors (notation, addition, dot product, cross product, unit vectors)
- Vectors in mechanics (relative position, force, moment, moment about an axis)
- Free Body Diagrams
- Force and Moment Balance
- 2- and 3-force bodies
- Trusses
- Center of Mass
- Structures and Machines
- Friction
- Fluid pressure
Strength of Materials

- Tension (stress, strain, elastic modulus, Poisson ratio,

thermal strain, indeterminate problems, stress on inclined sections)- Torsion (round elastic bars only, shear stress, torsional stiffness)
- Bending (symmetric elastic beams only, normal stress distribution, stiffness)
- V&M diagrams
- Beam deflection (determinate problems only)

In the fall of 2002 the coverage was reduced so that the following topics, which had been previously covered more or less depending on instructor or semester, are no longer consistently covered.

- Mohr's circle
- Buckling (but for the buckling lab which has been dropped in recent years also)
- Indeterminate bending problems (sometimes covered)
- distribution of shear stress in beams (VQ/It, sometimes skipped)
- distributed loads on bent cables and belt friction.

There is no argument about the importance and beauty of these topics, rather that it is better to cover less material better in ENGRD 2020 and leave these topics for later courses.

To further emphasize the importance of covering less material better, the number of lectures per week was raised in the spring of 2003 from 2 to 3 and the number of credits from 3 to 4.