Syllabus review

1. Syllabus review

2. Syllabus - objectives During this class You will • Learn about engineering profession and ethics governing engineers at work • Learn basic concepts of engineering • Learn open-ended problem solving skills through work on projects in engineering • Learn to work in teams • Learn to use a computational tool: Excel • Learn good engineering communication skills: written and oral Debates Lectures Homework In-class tasks Teardown project Design project

3. Syllabus - policies • Course policies: • Attendance is mandatory • You may miss 2 classes without penalty • Late work will not be accepted  • Plagiarism:   • Plagiarism is a serious offense • Follow ethics guidelines described in student handbook: http://www.umassd.edu/studenthandbook/academicregs/ethicalstandards.cfm • Students with Disabilities • In accordance with University policy, if you have a documented disability and require accommodations to obtain equal access in this course, please meet with the instructor at the beginning of the semester and provide the appropriate paperwork from the Disabled Students Services Office.  The necessary paperwork is obtained when you bring proper documentation to the Disabled Students Services Office (DSS), which is located in Group I, Room 016, phone: 508-999-8711.

4. Syllabus – schedule (cont’d)

5. Mass and Force

6. Agenda • Mass • Mass • Density • Mass Flow • Mass Moment of Inertia • Momentum • Force • Force basics and applications • Spring forces • Friction forces • Newton’s laws • Pressure

7. Mass • SI unit kg • Weight is a force, unit N • Mass is involved in multiple engineering principles! What is the mass of your calculator? How about its weight on Earth? And on Mars?

8. Agenda • Mass • Mass • Density • Mass Flow • Mass Moment of Inertia • Momentum • Force • Force basics and applications • Spring forces • Friction forces • Newton’s laws • Pressure

9. Density • Density=mass/volume • Important in e.g. material selection • Note: Density can change due to e.g. temperature and pressure Which one of these three materials would you choose for a part (size 0.001m3) of an airplane interior decor? How about as a counter weight for an elevator?

10. Lava Lamp Example www.google-store.com How does the lava lamp work?

11. Agenda • Mass • Mass • Density • Mass Flow • Mass Moment of Inertia • Momentum • Force • Force basics and applications • Spring forces • Friction forces • Newton’s laws • Pressure

12. Mass Flow • Mass flow = mass/time • Remember Volume Flow?

13. Volume or mass flow? • Depends on application • Volume flow preferred • when filling a tank of a specific volume with liquids of different densities • when a process can accept only a limited volume at a time • Mass flow preferred • in chemical reactions, where the number of reactant molecules (mass) is important • when measuring gas flow • When goods sold based on weight

14. Mass Flow - Task Estimate the mass flow of a gas pump. Density of regular gasoline is 720 kg/m3.

15. Agenda • Mass • Mass • Density • Mass Flow • Mass Moment of Inertia • Momentum • Force • Force basics and applications • Spring forces • Friction forces • Newton’s laws • Pressure

16. Mass Moment of Inertia m2 r2 • Measure of how hard it is to rotate something with respect to the center of rotation, or resistance to rate of change of rotation • For a single mass particle: • For a system of mass particles: z-axes r m

17. Mass moment of inertia - example Which one of the following object is harder to rotate around the z-axes? Both are made of steel (r=7860 kg/m3). z-axis R=5 cm h1=30 cm Ø=20 cm h1=4 cm

18. How are these related to mass moment of inertia? flywheel

19. Agenda • Mass • Mass • Density • Mass Flow • Mass Moment of Inertia • Momentum • Force • Force basics and applications • Spring forces • Friction forces • Newton’s laws • Pressure

20. Momentum • Momentum p (or L) • Momentum is directional • Velocity (a component of momentum) is directional

21. Momentum - Example www.aerospaceweb.org/question/investigations/columbia/foam-impact.jpg Investigators into the Columbia accident have estimated that the dislodged foam was about 48 x 29 x 14 cm (19 x 11.5 x 5.5 in) , weighed about 0.75 kg (1.7 lb) and impacted the Shuttle at nearly 850 km/h (530 mph). For the sake of a rough comparison, this block of foam would be about the same size and weight as a large loaf of bread. (www.aerospaceweb.org/question/investigations/q0131.shtml) p (or L) = mv = 0.75kg * 850,000m/3600s = 177 kg m/s Same momentum as a 5 kg (11 lb) brick hitting you driving 127.5km/h (80mph) !

22. Momentum - Task • Which has greater momentum? • An Olympic 100m runner at speed 10 m/s • A 1000kg car pulling out of a parking lot at 2 km/h

23. Mass and Weight • Mass - scalar (SI unit kg) • Weight – vector, it’s force (SI unit N)

24. Agenda • Mass • Mass • Density • Mass Flow • Mass Moment of Inertia • Momentum • Force • Force basics and applications • Spring forces • Friction forces • Newton’s laws • Pressure

25. Basics • Force is the interaction of two objects, typically one pushes or pulls the other • Direct contact: you pulling a door open • No direct contact: gravity pulling you toward the center of the earth • Force causes objects to move, lengthen, shorten, twist, bend, etc. • SI Unit: Newton [F]=N • F=ma  N=kg·m/s2 • U.S. Customary unit: pound force lbf • F=ma  lbf = 1slug·ft/s2 (1lbf=4.448 N)

26. Applications

27. Force is a vector quantity(on whiteboard) F1 F2

28. Agenda • Mass • Mass • Density • Mass Flow • Mass Moment of Inertia • Momentum • Force • Force basics and applications • Spring forces • Friction forces • Newton’s laws • Pressure

29. Spring Forces www.motorsportscenter.com/uploads/suspension.jpg www.pleasanthillgrain.com/bag_clip_bag_clips_stainless.asp http://rclsgi.eng.ohio-state.edu/~gnwashin/me481/mech_sys.html www.pharma-pen.com • Springs widely used in engineering • Store energy • Return to original position • Dampen vibration • Spring types: • Linear, torsional

30. Hooke’s law • Applicable in the elastic range of the spring • Elastic means there is no permanent deformation after the force is removed F = applied force (N) k = spring constant (N/mm, N/m) x = deformation of the spring (mm, m) x F

31. Whiteboard example • A compression spring is 10 cm long when no force is applied. When a force is applied, the deformed length is 8 cm. The spring has a spring constant of 10 N/m. Calculated the applied force.

32. Determining the spring constant • In-class task: determine the spring constant of one of the scales in the back of the room • Plot your data in Excel, explain all the steps you take • Prepare to present in front of the class • See EF example 10.1 for help F = applied force (N) k = spring constant (N/mm, N/m) x = deformation of the spring (mm, m)

33. Homework and Teardown • Homework – due Thursday 04/01 before the class • From the course book: 9.5 (10p), 9.6 (less than 1 page typed)(20p), 9.12 (10p), and 9.23 (10p) • Look for (broken) products to take apart later • good product will replace one bad assignment grade • Bring products early!

34. Agenda • Mass • Mass • Density • Mass Flow • Mass Moment of Inertia • Momentum • Force • Force basics and applications • Spring forces • Friction forces • Newton’s laws • Pressure

35. Friction Forces www.garageboy.com www.respo.net/respo_school/respo_school_006/pics/pour_oil_01.jpg • “Frictionless” systems, commonly used in physics, do not really exist • Friction can be useful • Types of friction: • Dry friction • Static friction • Dynamic (kinetic) friction • Viscous friction (fluid friction)

36. Applied force and friction Maximum static friction force Friction force (N) Dynamic friction force Applied force (N)

37. Whiteboard Example • The static coefficient of friction between an object and a horizontal surface is 0.85. The object’s mass is 0.550 kg. If the object is pushed on the surface (force horizontal) of 5N, will the object move?

38. Friction In-Class Task How would you calculate the static coefficient of frictionof your calculator starting to slide on your course book?

39. Agenda • Mass • Mass • Density • Mass Flow • Mass Moment of Inertia • Momentum • Force • Force basics and applications • Spring forces • Friction forces • Newton’s laws • Pressure

40. Free body diagrams • Free body diagram shows all external forces acting on the body. • Commonly used in statics, dynamics, and mechanics of materials • Steps to draw the free body diagram • Make a simplified drawing of the body in question • Draw all force vectors acting on it • Do not forget weight, unless gravitational forces are ignored • Label all forces • Define fore coordinate system

41. Practice (white board) • Steps to draw the free body diagram • Make a simplified drawing of the body in question • Draw all force vectors acting on it • Do not forget weight, unless gravitational forces are ignored • Label all forces • Define fore coordinate system

42. In-class task • Draw a free body diagram for the two pipes in a v-shaped channel. 40 20

43. Newton’s Laws • Every object in a state of uniform motion tends to remain in that state of motion unless an external force is applied to it • For every action there is an equal and oppositereaction

44. Newton’s Laws • Every object in a state of uniform motion tends to remain in that state of motion unless an external force is applied to it This also applies to an object in rest – they will not move unless acted upon by an unbalanced force Remember what happened to the cannon ball in both x and y-directions? 11m v0 vy0 a vx0 1.5m a 100m

45. Newton’s Laws • , Notice the relation between the magnitudes and directions of F and a! m

46. Newton’s Laws • , m

47. Newton’s Laws • S • s • For every action there is an equal and oppositereaction Both the magnitude and direction of the two forces are equal N m Why are the absolute value signs on N and g, not mg or m? mg

48. Force Basics - revisited • Force is the interaction of two objects, typically one pushes or pulls the other • Direct contact: you pulling a door (from the handle) open  the door pulling the handle so it does not come off • No direct contact: gravity pulling you toward the center of the earth  the surface of the earth (pavement?) pushing you so you do not sink in the earth

49. Team Assignment – Due Thu 10/17 12 noon • Problem/Design project: • Design a mass-spring system that can be taken to Mars to measure the acceleration due to gravity at the surface of Mars. • Explain the basis of your design • The governing equations & law’s of physics and how they relate to your design • Decisions on materials, components, attachment methods or working principle • Decisions that relate to the ability to take it to Mars • Include a drawing of your design • Include rough dimensions • Include a parts list. The level of detail can be “spring, glue, screw, metal plate”, so no need to find the actual part numbers and exact materials for the components. • Explain how your design should be calibrated and used • No need to build the system. • Hand in a report including equations and figures. The length can be anything from 2-4 pages typed. The length will not be graded. Only content is graded. Max 50p.

50. Assignment • Individual assignment (=homework) • Due Tue 10/22 12 noon • Problems: • 10.11, 10.15, 10.19, 10.21, 10.22 (10p each) • Follow format in course book EF chapter 4