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Engineering Test Review

MECHANICAL ADVANTAGE

FORCE, WORK, AND POWER

  • Force: A push or pull.

    • Effort Force: Input force generated by a person, motor, engine, magnetic field, spring, moving water, wind, or any phenomena imparting energy into a system. It is the force applied to the system.

    • Load (or Resistance) Force: Output force. It's the weight of the object to be moved or the resistance a mechanical device overcomes.

WORK

  • Work: Measure of energy transferred when a force acts on an object.

  • Displacement: How far an object moves along a straight line from start to finish. It's a vector quantity (magnitude and direction).

  • Distance: Measure of length, not confined to a straight line. It's a scalar quantity (magnitude only).

  • The formula for work is: W = Fd = (F \cos\theta)d , where:

    • W is work

    • F is the force

    • d is the displacement

    • \theta is the angle between the force and displacement vectors

WORK EXAMPLE

  • W = (F \cos \theta)d

  • W = (100 \text{ lbf}) (\cos 20^\circ) (12 \text{ ft})

  • W = (100 \text{ lbf}) (0.94) (12 \text{ ft})

  • W = 1128 \text{ lbf-ft}

POWER

  • Power: The amount of work accomplished per unit time.

    • Formula: P = \frac{W}{t}

    • Field unit of power: lbf-ft/sec

    • SI unit of power: watt

    • 1 \text{ horsepower} = 746 \text{ watt}

    • 1 \text{ watt} = 0.738 \text{ lbf-ft/sec}

POWER EXAMPLES

  • Example 1:

    • P = \frac{W}{t} = \frac{1128 \text{ lbf-ft}}{20 \text{ s}} = 56.4 \text{ lbf-ft/sec}

    • 56.4 \text{ lbf-ft/sec} / 0.738 = 76.5 \text{ Watts}

  • Example 2:

    • t = 20 \text{ hr} \times \frac{3600 \text{ sec}}{\text{hr}} = 72,000 \text{ sec}

    • P = \frac{W}{t} = \frac{1128 \text{ lbf-ft}}{72,000 \text{ sec}} = 0.016 \text{ lbf-ft/sec}

    • 0.016 \text{ lbf-ft/sec} / 0.738 = 0.022 \text{ Watts}

MECHANICAL ADVANTAGE

  • Gain in force or distance due to simple or compound machines.

  • Ratio of output force produced by a machine to the input force applied to it.

  • Two types of Mechanical Advantage (MA):

    • Ideal Mechanical Advantage

    • Actual Mechanical Advantage

IDEAL MECHANICAL ADVANTAGE (IMA)

  • Theory-based, friction is not considered.

  • Used in efficiency and factor of safety design calculations.

  • Ratio of distances traveled.

  • IMA = \frac{d\text{effort}}{d\text{load}} = \frac{de}{dl}, or \frac{di}{do}, or \frac{Li}{Lo}

ACTUAL MECHANICAL ADVANTAGE (AMA)

  • Inquiry-based (testing), friction is considered.

  • Used in efficiency calculations.

  • Ratio of force magnitudes.

  • AMA = \frac{F\text{out}}{F\text{in}} = \frac{Lo}{Li}

EFFICIENCY

  • Ratio between the amount of work that goes into and comes out of a machine.

  • No machine is 100% efficient.

  • \text{Efficiency} = \frac{\text{Work Output}}{\text{Work Input}} \times 100

  • \text{Efficiency} = \frac{AMA}{IMA} \times 100 = \frac{h}{H}

SIMPLE MACHINES

  • Used to make work easier.

  • A mechanical device that changes the direction or magnitude of a single applied force.

  • Six Simple Machines:

    • Inclined Plane

    • Wedge

    • Lever

    • Wheel & Axle

    • Pulley

    • Screw

LEVERS

  • A rigid bar that rotates about a pivot point called the fulcrum.

  • Used to move a load when an effort force is applied.

  • Formula: MA = \frac{dl}{de} = \frac{he}{hl}

  • Three Classes of Levers:

    • 1st Class

    • 2nd Class

    • 3rd Class

1st CLASS LEVERS

  • Fulcrum is located between the effort and the load.

  • Examples shown in diagrams.

2nd CLASS LEVERS

  • Load and effort force act in opposite directions.

  • The load is always located between the fulcrum and effort.

  • The MA of a 2nd class lever will always be greater than 1.

  • Examples given in the slideshow.

3rd CLASS LEVERS

  • Load and effort forces act in opposite directions.

  • The effort is always located between the fulcrum and the load.

  • The MA of a 3rd class lever will always be a value between 0 and 1.

  • Examples given in the slideshow.

LEVER SUMMARY

Feature

1st Class

2nd Class

3rd Class

Force

LEVER EXAMPLE

  • \text{Efficiency} = (\frac{AMA}{IMA}) \times 100

  • Given: 90% efficient, Effort = 150 lb, Load = 8 ft, Fulcrum = 4 ft

PULLEY

  • A free-spinning wheel around which a rope, chain, or belt is passed.

    • IMA = \text{# of support cables} = \frac{Dh}{Dh}

  • Three Types of Pulleys:

    • Fixed Pulley

    • Moveable Pulley (Runner)

    • Block and Tackle (Compound pulley system)

FIXED PULLEY

  • IMA = 1

  • 1 Support Cable

  • Load and effort forces are applied on either end of the pulley wheel.

  • NOTE 1: “Support” cables ALWAYS act in the direction OPPOSITE to the load!

  • NOTE 2: Support cables are ALWAYS counted in reference to the same block.

  • NOTE 3: We ALWAYS count the support cables of pulleys that are bearing the load.

MOVEABLE PULLEY (RUNNER)

  • IMA = 2

  • 2 Support Cables

  • Both cables support the load.

BLOCK & TACKLE PULLEY (COMPOUND PULLEY)

  • IMA = \text{# OF STRANDS}

  • Arrangement of two or more pulleys strung together to lift or move a load.

  • IMA = 2 in the example image.

BLOCK & TACKLE PULLEY (BLOCK SYSTEM)

  • Pulley that contains multiple wheels that spin independently but move in unison.

BLOCK & TACKLE PULLEY EXAMPLE

  • Given: 60 lb load, Vertical distance of load = 10 ft, Actual effort force = 15 lbs

    • IMA = \text{# of support cables}

    • \text{Efficiency} = (\frac{AMA}{IMA}) \times 100

    • AMA = \frac{Lo}{Li} = \frac{60}{15} = 4

Civil Engineering

  • Deals with the design, construction, and maintenance of the physical and naturally built environment.

  • Transportation engineering: Focuses on planning, designing, operating, and maintaining transportation systems.

  • Environmental engineering: Applies engineering principles to improve and maintain the environment.

  • Geotechnical engineering: Involves studying the behavior of earth materials and applying this knowledge to the design and construction of foundations.

  • Construction engineering: Deals with the planning, design, and management of construction projects.

  • Water resource engineering: Deals with the arrangement and management of water.

  • Earthquake engineering: Concentrates on mitigating potential hazards involving earthquakes for civil structures.

  • Structural engineering: Analyzes and designs safe, load-bearing structures that can withstand significant stress.

  • Coastal engineering: Concerned with the management and protection of coastal areas from floods, erosion, and other environmental factors.

  • Traffic engineering: construction of roads, highways and tunnels using basic techniques like planning, designing, and construction.

  • Surveying engineering: Deals with surveying and leveling of lands using various instruments, mapping & contouring of terrains

  • Marine engineering: The design of offshore structures.

  • Sanitary engineering: application of engineering methods to improve sanitation of human communities

  • Design engineering: focused on the engineering design process in any of the various engineering disciplines and design disciplines

  • Forensic engineering: identifying what went wrong by applying civil engineering concepts

Mechanical Engineering

  • the study of physical machines that may involve force and movement.

  • Automotive engineering: Designing and developing power-producing machines

  • Mechatronics: focuses on the integration of mechanical engineering, electrical engineering, electronic engineering

  • Aerospace engineering: the primary field of engineering concerned with the development of aircraft and spacecraft

  • Robotic engineering: study and practice of the design, construction, operation, and use of robots

  • Thermodynamics engineering: a field that focuses on how heat relates to energy.

  • Fluid mechanics: the branch of physics concerned with the mechanics of fluids and the forces on them.

  • Combustion engineering: a specialty that focuses on energy generation, propulsion, heating and waste disposal.

  • Energy engineering:a broad field of engineering dealing with areas such as energy harvesting and storage, energy conversion, energy materials, energy systems, energy efficiency, energy services.

  • Materials science and engineering: an interdisciplinary field of researching and discovering materials.

Electrical Engineering

  • the study and application of electricity, electronics, and electromagnetism

  • Control engineering: deals with control systems, applying control theory to design equipment and systems

  • Computer engineering: integrates several fields of computer science and electronic engineering required to develop computer hardware and software.

  • Instrumentation and control engineering: studies the measurement and control of process variables, and the design and implementation of systems that incorporate them.

  • Signal processing engineering: focuses on analyzing, modifying and synthesizing signals.

  • Electronic engineering: distinguished by the additional use of active components such as semiconductor devices to amplify and control electric current flow.

  • Microelectronics engineering: relates to the study and manufacture of very small electronic designs and components

  • Process engineering: the understanding and application of the fundamental principles and laws of nature that allow humans to transform raw material and energy into products that are useful to society.

  • Telecommunications engineering: the transmission of information with an immediacy comparable to face-to-face communication.
    *Project engineering: designs, tests, and manages the development of any form of electrical equipment

Chemical Engineering

  • an engineering field which deals with the study of operation and design of chemical plants as well as methods of improving production.

  • Biochemical engineering: also known as bioprocess engineering, is a field of study with roots stemming from chemical engineering and biological engineering.

  • Environmental engineering: a professional engineering discipline related to environmental science.

  • Physical chemistry engineer: the study of macroscopic and microscopic phenomena in chemical systems in terms of the principles, practices, and concepts of physics such as motion, energy, force, time, thermodynamics, quantum chemistry, statistical mechanics, analytical dynamics and chemical equilibria.

  • Fluid dynamics engineer: subdiscipline of fluid mechanics that describes the flow of fluids — liquids and gasses

  • Chemical reaction engineering: a specialty in chemical engineering or industrial chemistry dealing with chemical reactors

  • Biotechnology engineering: a multidisciplinary field that involves the integration of natural sciences and engineering sciences in order to achieve the application of organisms and parts.

  • Biochemistry engineering: the study of chemical processes within and relating to living organisms.

  • Electrochemistry engineering: the branch of physical chemistry concerned with the relationship between electrical potential difference and identifiable chemical change.

  • Petroleum engineering: a field of engineering concerned with the activities related to the production of hydrocarbons, which can be either crude oil or natural gas.
    *Process control engineering: a system used in modern manufacturing which uses the principles of control theory and physical industrial control systems to monitor, control and optimize continuous industrial production.

Engineering Design Process

Define the Problem: Clearly identify what needs to be solved, for whom, and why it's important. This includes understanding the user's needs, identifying constraints (e.g., budget, time, materials), and establishing success criteria.

Do Background Research: Gather information about the problem, existing solutions, relevant scientific principles, and potential challenges. This helps avoid reinventing the wheel and informs potential approaches.

Brainstorm Solutions (Imagine): Generate a wide range of possible solutions without immediate judgment. Encourage creative and diverse thinking to explore many alternatives.

Select the Best Solution (Plan): Evaluate the brainstormed ideas against the defined requirements and constraints. Choose the most promising solution or combination of ideas based on feasibility, potential impact, and resource considerations. Develop a detailed plan for the chosen solution.

Develop the Solution & Build a Prototype (Create): Refine the chosen design, create detailed drawings or schematics, and then build a preliminary model or prototype. This tangible version allows for testing and verification of the design.

Test and Evaluate: Thoroughly test the prototype to see how well it works and if it meets the established criteria. Collect data and analyze the results.

Improve (Redesign as Needed): Based on the testing results, identify areas for improvement. Modify the design, make necessary changes, and repeat the testing process. This iterative cycle of testing and refining continues until a satisfactory solution is achieved.