# Mechanics and Strengths

**MECHANICS/STRENGTHS**

SMS Code EE401001

Level 4 Credits 14

Total Hours 140 Contact Hours 92

Work Experience Hours Nil Self Directed Hours 48

NQF Units/Other Components contained are:

**Aims**
The general aim of this paper is to relate topics of Mechanical Engineering to the field of physics and to provide students with the basic fundamental principles of mechanics of machines. This course will also introduce the students to the basic fundamental principles of strengths of materials.

**Learning Outcomes**
At the successful completion of this course, students will be able to:
• derive the basic SI units of mass, force, density, relative density and moments
• analyse and solve basic static force systems
• understand the concept of and calculate the centre of gravity
• demonstrate an understanding of the concept of friction and its effects on mechanical systems
• demonstrate an understanding of the concept and practical applications of the laws of the machine
• use their basic knowledge of dynamics, momentum, impulse, work, power and energy to solve problems in linear and rotary systems
• define and specify the basic units of stress, strain and shear.
• calculate second moment of area for various shapes.
• specify and calculate the basic properties of engineering materials.
• calculate basic stresses and strains.
• calculate basic beam loads, reactions, shear forces and bending moments. draw basic shear force and bending moment diagrams.
• prove the beam bending stress formula and calculate bending stresses, section modulus and plot the bending stress distribution across the beam.
• prove the torsional shafting stress formula and calculate torsional stress, torsional rigidity and plot the torsional stress distribution across the shaft.

**Content**
Mechanics
basic mechanics (SI units - fundamental, supplementary and derived units, mass, force, density, relative density, moments
static’s (vector analysis, parallel forces, equilibrium)
static force systems (free body diagrams, Bows notation, polygon of forces)
Moments of forces
pin jointed frameworks (graphical solutions method of joints, method of sections)
centre of gravity, centre of area
Friction
coefficient of friction
friction on inclined plane
friction in screws and wedges
Machines
load effort
mechanical advantage, velocity ratio
machines like levers, blocks, screws, gears, differential pulleys
Dynamics (basic)
linear motion - displacement, velocity, acceleration
vertical motion under gravity
rotary motion - displacement, velocity, acceleration
relation between linear and angular motion

Momentum and Impulse
Newton’s laws
relation between force, mass and acceleration
Work, Power and Energy
linear and rotational
energy forms and conservation
power, work done and diagrams
Dynamics (intermediate)
moment of inertia, radius of gyration
centrifugal and centripetal forces and acceleration
torque, power, angular momentum
vehicle dynamics, hoists, flywheels
Principles of Strengths of Materials
definitions/units of stress, strain, shear
basic stress strain calculations
2nd Moment of Area
parallel axis theorem
neutral axis
polar moment of area
Mechanical Properties of Materials
tension compression test, yield/ultimate stress
stress- strain diagram
stress-strain behaviour of ductile and brittle materials
Hooks law, Poison's ratio, Young's modulus
Simple Stress and Strain
tensile, compressive, shear stress and strain
factor of safety
stresses in thin cylinders
stresses in composite bars
strain and shear strain energy
Beams (basic)
reactions, equilibrium
shear force and bending moment diagrams (point and udl loads) simply supported, cantilever
Bending Stresses
proof of bending equation
bending stress distribution
section modulus, selection of sections from tables
Torsional stress
proof of shafting formula
torsion in solid and hollow shafts
torsional stress distribution on a circular shaft
torsional rigidity
combined bending and torsion in shafts
**Learning/Teaching Methods**
Lecturers will use a range of teaching and learning methods with a strong focus on activities. See section 5.8.2 for further details.

**Assessment**
Assessment is the general term used for activities, which provide feedback on Student performance and is the measure by which a student’s performance is determined. The types of assessment used in papers are:
• Practical assignments and exercises
• Practical and laboratory work evaluations as individual or group project
• Tests
• Examinations

Final examinations may include any material studied throughout the course. 2 Examinations 50% Tests 10% Assignments 10% Laboratories 30%

Attendance Requirements 90%

Completion requirements To complete this course, students must meet the attendance requirement and pass all summative assessments.

Literature References for Curriculum Development
Bolton, W. (1994). *Engineering Science* (2nd Ed). Oxford Boston: Newnes.

Student Reading List