Unit 6 Competency 1 - Explore concepts associated with physical principles of engineering
Suggested Objective a: Identify the engineering design cycle
According to NASA, below is the engineering design process. The information below along with the image above are copied from http://www.nasa.gov/audience/foreducators/plantgrowth/reference/Eng_Design_5-12.html#.VF0qX_nF98E Links to an external site. on November 7, 2014.
The engineering design process involves a series of steps that lead to the development of a new product or system. In this design challenge, students are to complete each step and document their work as they develop their lunar plant growth chamber. The students should be able to do the following:
STEP 1: Identify the Problem - Students should state the challenge problem in their own words. Example: How can I design a __________ that will __________?
STEP 2: Identify Criteria and Constraints - Students should specify the design requirements (criteria). Example: Our growth chamber must have a growing surface of 10 square feet and have a delivery volume of 3 cubic feet or less. Students should list the limits on the design due to available resources and the environment (constraints). Example: Our growth chamber must be accessible to astronauts without the need for leaving the spacecraft.
STEP 3: Brainstorm Possible Solutions - Each student in the group should sketch his or her own ideas as the group discusses ways to solve the problem. Labels and arrows should be included to identify parts and how they might move. These drawings should be quick and brief.
STEP 4: Generate Ideas - In this step, each student should develop two or three ideas more thoroughly. Students should create new drawings that are orthographic projections (multiple views showing the top, front and one side) and isometric drawings (three-dimensional depiction). These are to be drawn neatly, using rulers to draw straight lines and to make parts proportional. Parts and measurements should be labeled clearly.
STEP 5: Explore Possibilities - The developed ideas should be shared and discussed among the team members. Students should record pros and cons of each design idea directly on the paper next to the drawings.
STEP 6: Select an Approach - Students should work in teams and identify the design that appears to solve the problem the best. Students should write a statement that describes why they chose the solution. This should include some reference to the criteria and constraints identified above.
STEP 7: Build a Model or Prototype - Students will construct a full-size or scale model based on their drawings. The teacher will help identify and acquire appropriate modeling materials and tools. See the design brief for a sample list.
STEP 8: Refine the Design - Students will examine and evaluate their prototypes or designs based on the criteria and constraints. Groups may enlist students from other groups to review the solution and help identify changes that need to be made. Based on criteria and constraints, teams must identify any problems and proposed solutions.
The Engineering Design Cycle - Part 1
Links to an external site.
Suggested Objective b: Recognize the importance of maintain an engineering notebook
An engineer's notebook is a book in which an engineer will formally document, in chronological order, all of his/her work that is associated with a specific design project. Look at the PowerPoint below from Fremont that explains more in depth about an engineer's notebook. It was retrieved from www.fremont.k12.ca.us/cms/lib04/.../Engineers_Notebook.ppt on November 7, 2014. Take notes as needed.
Engineers_Notebook.ppt Download Engineers_Notebook.ppt
Warren Harrison at Web CECS PDX.edu provides the following guidelines for an engineering notebook.
The Engineering Notebook
Engineering notebooks are used in industry to record what work was done in case the engineer leaves the project and his/her replacement needs to quickly get up to speed as well as when work was done for patent and copyright purposes. If properly done, an Engineering Notebook permanently records what was done on a project, and particularly what inventions were made and when. Properly maintained Engineering Notebooks are frequently used to document patent claims, since patents are granted to the first person to invent something, not the first person to file for the patent.
The basic guidelines are:
- Notebooks must be permanently bound. Notebooks in which a page can be unobtrusively added or removed such as a three-ring binder are not acceptable as an Engineering Notebook
- Every page must be numbered consecutively, to prove that you have not added or removed pages after the fact.
- Either one side of each page or both sides of each page may be written on, but it must be done consistently. If only one side of each page is used, a line should be drawn through the blank backs of each page.
- Everything must be written in permanent ink. Either blue or black may be used, but a pencil should never be used since pencil can be erased.
- Notebooks must be clearly labeled with the author's name, the team's name, and the term. Devote this Engineering Notebook to the Capstone Project - they will need to be turned in at the end of the project.
- Leave several pages at the beginning for a table of contents so you can locate key information quickly.
- Entries should be made in chronological order.
- Start a new page each day you work on the project. At the top of the page clearly indicate the date and hours you worked. Either write out pr abbreviate the month to avoid confusion (is 08/02/02 August 2, or is it February 8?).
- At the end of the day draw a line through any space left on the page and the next day begin on a new page.
- Do not leave any blank pages - if a page is left blank, draw a line through the entire page.
- All data is to be recorded directly into the notebook. Notes and calculations should be done in the notebook, NOT on loose paper.
- In the case of an error, to keep from obliterating the original text, draw a single line through the incorrect item. Do not erase or use correction fluid. Initial and date all corrections.
- If information is summarized or rewritten elsewhere, a reference to that page should also be written next to the lined-out text.
- All work done by the author relating to the project, including web surfing, readings, research, design, coding, documentation, testing, team work meetings, sponsor meetings, status meetings with the instructor, etc. should be described. Copies of e-mails, memos, code listings, etc. should be stored in a three ring binder. These pages should be numbered and dated and a reference to them should appear under the corresponding date in the Notebook.
- The notebook is meant to be a permanent record of what has been done. It must be neat enough for someone else to understand what has been done a year or more later. On the other hand, it need not be a polished document - these are the author's notes, not a document intended for publication.
- The material written into the Notebook should not be transcribed from another piece of paper - to be credible, the Notebook must reflect the author's original notes.
Most companies require that someone besides the author date and sign the Notebook on a daily or weekly basis as proof of when the work was done. If there is some potential that the work being done on the Capstone project may have some value, students should have the instructor sign and date the pages on a weekly basis so it can be legally established when the work was done. In addition to signatures to verify dates, additional evidence is important if a major breakthrough or discovery is recorded. Witnesses that both observed as well as understand the work should sign their signatures under the caption "performance observed and understood by ... "
A patent requires that an invention be both "conceived" as well as "reduced to practice". The Notebook must show there no abandonment of the idea between the time it is conceived and when it is reduced to practice. Negative notes such as "No good" or "Doesn't work " might be construed as indicating the idea was abandoned.
Retrieved from http://web.cecs.pdx.edu/~warren/Capstone/index.cgi?PAGE=engineering_notebook Links to an external site. on November 7, 2014
Engineering Notebook
Links to an external site.
10 Step Engineering Design Process
1) Identify the problem or product innovation
2) Define the working criteria and goals
a) Specify parameters and constraints to better define the need or problem
3) Research and gather data
a) Examine current state of the issue and current solutions
b) Explore other options via the internet, databases, interviews, etc.
4) Brainstorm and generate creative ideas
a) Draw on mathematics and science
b) Generate a unique, custom-made solution "from scratch,", find an "off-the-shelf" solution that someone else has used to solve a similar problem or find existing products to combine and adapt.
5) Analyze possible solution(s)
a) Will it do what I need done?
b) Articulate the possible solutions in two and three dimensions
c) Perform a cost/benefit analysis
d) Refine the possible solutions
6) Develop and test models
a) Model the selected solution(s) in two and three dimensions
b) Does it work?
c) Does it meet the original design constraints?
d) Perform laboratory testing
7) Make a decision
a) Select the best possible solution(s)
b) Determine which solution(s) best meet(s) the original requirements
8) Communicate and specify
a) Design drawings
b) Written report or presentation that includes a discussion of how the solution(s) best meet(s) the needs of the initial problem.
c) Information on parts, processes, materials, space facilities, components, equipment, machinery and systems involved in manufacturing.
d) Discuss societal impact and trade-offs of the solution(s)
9) Implement and commercialize
10) Perform post-implementation review and assessment
Engineers design products and processes based on:
-Economics
-Social Implications
-Aesthetics
-Client preference
-Technical & non-technical constraints
-Safety
-Resources
-Environment
Suggested Objective c: Demonstrate how physics affects robots by exploring topics such as weight, torque, mass, and center of gravity
Weight is the body's relative mass or the quantity of matter contained by it, giving rise to a downward force or the heaviness of something.
Torque is the twisting force that tends to cause rotation.
Mass is the property of a physical body related to its relative density and volume.
Center of gravity is a point at which the entire weight of a body may be considered as concentrated so that if supported at this point, the body would remain in equilibrium in any position.
Definitions taken from the Merriam Webster dictionary online on November 7, 2014.
Difference between Mass and Weight Links to an external site. from Khan Academy Videos
Introduction to Torque
Links to an external site.
Centre of Gravity
Links to an external site.
Mass and Weight Links to an external site.
Units and Standards
Units are the measurement of any quantity is made relative to a particular standard. For example, a meter for distance and the second for time. A standard defines exactly how long one meter or one second is and are needed to make an accurate measurement.
Measuring: English vs Metric Units
Measurements are ways that we can communicate to others the quantity of something. There are two standards of measuring things, English and Metric Units.
English units are used only in the United States. Some common English units are:
| Distance | ||||||
| Inches (in) | 12 in | = | 1 ft | |||
| Feet (ft) | 3 ft | = | 1 yd | |||
| Yards (yd) | 1760 yd | = | 1 mi | |||
| Miles (mi) | 1 mi | = | 5280 ft | |||
| Weight | ||||||
| Ounces (oz) | 16 oz | = | 1 lb | |||
| Pounds (lb) | 2000 lb | = | 1 t | |||
| Tons (t) | 1 t | = | 2000 lb | |||
| Volume | ||||||
| Teaspoons (tsp) | 3 tsp | = | 1 tbsp | |||
| Tablespoons (tbsp) | 1 tbsp | = | 3 tsp | |||
| Fluid ounces (fl oz) | 8 fl oz | = | 1 cup | |||
| Cups (c) | 2 cups | = | 1 pt | |||
| Pints (pt) | 2pt | = | 1qt, | 8 pt | = | 1 gal |
| Quarts (qt) | 4 qt | = | 1 gal | |||
| Gallons (gal) | 2 gal | = | 1 peck | |||
| Pecks | 4 pecks | = | 1 bushel | |||
| Bushels | 1 bushel | = | 4 pecks | |||
| Temperature | ||||||
| Degrees Fahrenheit (°F) | ||||||
| Speed | ||||||
| Miles per hour (mph) |
These units should look somewhat familiar to you. I bet you are thinking since we live the US, you only need to know English units, right? It's very important that we as Engineers speak the same language mathematically. If you don't think speaking the same language mathematically is important, check here
Links to an external site. to see some real world implications of miscommunication of something as simple as units.
Everyone else uses the Metric system, so let's examine it more in depth. The metric system is divided into different categories of measurement like the English system, but it has a base unit for each category. A base unit means all other terms of measurement are built from that unit.
Here are some common metric units:
| Distance | ||||||
| Millimeter (mm) | 1000 mm | = | 1 m | |||
| Centimeter (cm) | 100 cm | = | 1 m | |||
| Meter (m) | base unit (1) | |||||
| Kilometer (km) | 1000 m | = | 1 km | |||
| Weight | ||||||
| Milligrams (mg) | 1000 mg | = | 1 g | |||
| Grams (g) | base unit (1) | |||||
| Kilograms (kg) | 1000g | = | 1 kg, | 1000 kg | = | 1 t |
| Metric ton (t) | 1000 kg | = | 1 t | |||
| Volume | ||||||
| Milliliters (mL) | 1000 mL | = | 1 L | |||
| Liters (L) | base unit (1) | |||||
| Temperature | ||||||
| Degrees Celsius (°C) | ||||||
| Speed | ||||||
| Meters per second (m/s) |
This information will be very useful to copy into your Engineering Notebook because you will refer to it frequently throughout this course and many other science courses. As we learn more of the principles of physics, we will add to this list.
Center of Gravity
The earth exerts a gravitational force upon all objects close to it. This force is called gravity. The force of gravity acting on an object is called its weight. The force of gravity or weight effectively acts on object’s center of gravity. The term center of gravity is used interchangeably with center of mass. For a symmetrical object the center of mass is located at the geometric center of the object.
When an object is supported at its center of gravity, it is balanced. Center of gravity is very important to the stability of robots. A robot is stable when the center of gravity is within the base of the robot.
When an object is thrown in the air, its center of gravity will follow a parabolic path. The figure below shows a portion of a wrench at it is tossed in the air. The center of gravity of a wrench follows a parabolic path. The rest of the wrench rotates around the center of gravity.
Center of Gravity Outside of Physical Structure of Object
The center of gravity of an object can exist where there is no mass. A donut's center of gravity is at its center where there is no mass. Other objects that have their center of gravity outside their physical structures include an empty pan or cup, a chair, or a boomerang.
The objects below have center of masses in mid-air.
Toppling
An object is stable when the center of gravity is contained in the base of the object. If the center of gravity falls outside the base the object will topple over. In the drawing below the center of gravity is shown by the plumb line. An object will topple once its plumb line falls outside of its base of support. The figure below shows a block being toppled over once its plumb line falls outside the base of the box.
Applications
Keeping the Leaning Tower of Pisa from toppling is an engineering problem.
- The center of mass of a human body is at the pelvis area.
- The center of mass of the solar system (when all planets are aligned collinearly) is about 2 solar radii from the sun’s center.
- The center of mass of a rectangle is at the intersection of the two diagonals.
- Alexander Calder, the inventor of mobiles, is famous for his sculptures that allow gusts of wind to arrange their elements. The structures of his mobiles are rearranged but the center of gravity always falls within the base of support (i.e. the pivot point).
- Archimedes introduced the concept of center of gravity. He demonstrated that a single point on a lever is exerted the same amount of torque as weights resting at various points of the lever. He also developed methods to find centers of masses of regular shapes such as a triangle and hemisphere.
- There are three trucks parked on a hill. The center of mass of each truck is marked with an “x”. Out of the three, which truck(s) would topple over?
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A bottle rack that seems to defy common sense is shown in the figure. Where is the center of gravity of the rack and bottle?
Solutions
- Only the first truck will topple over. Draw a plumb line from the center of mass of each truck to the ground. Only the first truck’s plumb line falls out of its base of support.
- The center of gravity is at point of the bottle directly above the base of support of the rack on the table. The center of gravity is over where the rack stands. It does not tip over because there is a support beneath it.
Some parts of this page were adapted from High School Online Collaborative Writing: Center of Mass (http://schools.wikia.com/wiki/Center_of_Mass Links to an external site.)
Linear Motion is motion along a straight line. The analog of linear motion is circular motion, which we will learn more about in depth in the next few pages.
The key concepts of linear motion: (Please click on each link and complete the interactive lesson)
Scalars and Vectors Links to an external site.
Distance vs Displacement Links to an external site.
Speed and Velocity Links to an external site.
Acceleration Links to an external site.
Rotational Motion
Click here Links to an external site. for an interactive lesson on Rotational Motion.
Torque
Watch this NBC Learn: The Science of football Links to an external site.video to learn more about torque.
Resources:
http://hyperphysics.phy-astr.gsu.edu/hbase/torq.html Links to an external site.