1. Mechanics

2. Vectors intwodimensions 3. Physical quantity havingmagnitude and a unit but not direction.DocScientia p. 12Scalar definition 4. Physical quantity havingMagnitude, unit anddirection.DocScientia p. 12 Vector definition 5. Graphical representation of vectorsDocScientia p. 12 6. blength end (head) astart (tail)DocScientia p. 12 7. Division of a vector intocomponentsDocScientia p. 12 8. one dimension vectors: straight line to thevertical or horisontalaxesDocScientia p. 12 9. two dimension vectors:form an angle to the axesDocScientia p. 12 10. components of a force at an angle: divided into 2 parts, 2 vectors at , same effect as original vectorDocScientia p. 12 11. Fy FFx = FcosFy = Fsin r y Cos = x/r = Fx/F Sin = y/r = Fy/F x FxDocScientia p. 13 12. Object on slopes experienceforces like gravity that are not or to plane DocScientia p. 14 13. Forces are divided with respect to the plane.DocScientia p. 13 14. Trig functions calculate the componentsDocScientia p. 13 15. cos = x/r = Fg/Fg sin = y/r = Fg/Fg Fg = FgcosFg Fg = Fgsin r xFg FgDocScientia p. 14y 16. Pull or pushWhat isa force Vector F NLength = size = direction of forceDocScientia p. 20 17. forcesnon-contact Aact over a distancecontact Bobjects are in contactwith each otherDocScientia p. 20 18. non-contact forces Aact over a distanceMagnetic forces 1 Electrostatic forces 2 Gravitational forces 3DocScientia p. 21 19. contact forces Bobjects are in contactwith each otherApplied forces 1Friction 2Normal forces3DocScientia p. 21 20. contact forces Bobjects are in contactwith each otherTension4Air friction 5 Compression 6DocScientia p. 21 21. contact forces Bobjects are in contactwith each otherApplied forces 1Same line as direction of motionORAt an agle to the direction of motionDocScientia p. 21 22. contact forces Bobjects are in contactwith each otherFriction 2f or Ff tries to minimise motion, opposite direction to the movement to contact surfaceDocScientia p. 21 23. DocScientia p. 21 24. B 1 Same line as direction of motion OR At an agle to the direction of motionFg FyFxFgDocScientia p. 21 25. contact forces Bobjects are in contactwith each otherNormal forces (FN) 3Force exerted by a surface on an objecton that surfaceAlways perpendicular to the surfaceSupporting force is equal and opposite tothe force of the objectDocScientia p. 21 26. contact forces Bobjects are in contactwith each other Tension (FT) 4Pulled cable/rope = tensionTension is constantTwo directionsMass = negligible, if asked to add:Gravitational force will act on thecenter of the ropeDocScientia p. 22 27. contact forces Bobjects are in contactwith each otherAir friction (Fair) 5Offer resistance to objects movingthrough airActs in the opposite direction tomovementDocScientia p. 22 28. contact forces Bobjects are in contactwith each otherCompression (Fspring) 6 Equal in magnitude, exerted on any object touching the springDocScientia p. 22 29. Forces and free body diagramsDocScientia p. 22 30. FNF FNFo r fF Fer f ec Fge b Fg o Object represented asd a dot can be a bit bigd Object w all forces y All forces = arrows wi Simplify as block magnitude anda Arrow shows d directiong magnitude and i Arrows point awaydirection a from the dotr Arrow at position g Force @ angle isa where force isr represented by eitherm exerted a the force itself ORDocScientia p. 22 m components 31. Friction forceDocScientia p. 28 32. Contact forceTwo objects in close contact, and it tries to move acrosseach other.Surface of solids = generally rough.DocScientia p. 28 33. Uneven sections hook on each other when sliding.Friction = opposes motionof two surfaces.DocScientia p. 28 34. Factors thatinfluence the size of the frictionalDocScientia p. 29 forceSurface type Normal force 35. FN = Fg = wFx = FcosFx = Fcos F Fy = FsinNormal NFy = Fsin FN = Fg Fy forceFN = Fg + Fy FgFN FNFg FyFg=FgsinFxFg=Fgcos Fy FN=Fgcos FxDocScientia p. 30 Fg 36. Surface type Smooth tiles are very slipperySlightly melted ice onan ice rink it is easyto glideDocScientia p. 31 37. Surface type The rougher the surface,the greater thefrictionDocScientia p. 31 38. The extent they affectSurface one another is type represented by thecoefficientof friction ()DocScientia p. 31 39. Coefficient of frictionDocScientia p. 31 40. Symbol: No unit factor of roughness Surface pairs have twocoefficients:static friction: s kinetic friction: kDocScientia p. 31 41. Proportionality constant ofThe relationship fF is knownNas the coefficient of frictions max > k The smaller the , the less the resistance offered by asurface, value < 1DocScientia p. 31 42. How to reduce frictionDocScientia p. 31 43. Lubricate:OilGrease Finely powdered graphiteWet the surface with waterDocScientia p. 31 44. Frictional force of one contact surfaceon another when there is no relative motionbetween the objectsDocScientia p. 32Static friction (fs) 45. Independent of surface areaDependent on mass & weight mass + weight = FNDepends on nature of surfacesActs opposite to motionDocScientia p. 32 46. Directly proportional to the normal forceDocScientia p. 32 47. Frictional force of one contact surfaceon another when one or bothobjects are movingDocScientia p. 32Kinetic friction (fk) 48. Independent of surface areaDependent on mass & weight mass + weight = FNDepends on nature of surfacesActs opposite to motionDocScientia p. 32 49. Smaller than fs(max)Directly proportional to the normal forceDocScientia p. 32 50. Applied force, no motion: fs = FappliedApplied force increased, on the vergeof motion:An object fssFN and fs(max)=sFNfs(max) = FTat rest on a but mass is the sameNo horisontal force: fs(max) = sFNFg, FN, fs are Fapplied = 0 Nrough unchangedThus fs = 0 N FNhorisontalsurface FT FTffDocScientia p. 33 W 51. AppliedApplied force. @ angle:When it force > fs(max)Object begins to move. FN: FN = Fg FyGet componentsfinally FrictionNonow kinetic. fk = FNis vertical force Applied push @ angle:fk=kGetfk = (F F ) = F + F FN c mponentsstarts to ogNy g No vertical motion: fk = FNymovefk = (Fg + Fy)on aFNFT FFTThorisontalsurface fWDocScientia p. 34 52. @ rest: fssFN accelerating:Graph of fs=sFN fwhen anFrictional force f (N)About to startmovingfs(max) = sFs Fk constantobject starts tomove over arough surface Applied force FT (N)DocScientia p. 35 53. Object at rest: Fg=FgsinFgand fs: equal andAn objectFg=Fgcosopposite, fs=Fgsinat rest on arough fs(max)=sFN FNsurface fs(max)=s(Fgcos)@ an FgfsanglFge wDocScientia p. 35 54. Object at rest: Fg=FgsinOBJECT SLIDING Fg=FgcosMoving F fand F F ININ THEandf resistanceForward applied forceincreases Net force = forwardPlane will accelerate forwardDocScientia p. 44 63. Is the vector of all the forces acting on the object.One force with thesame effect as all the other forces together.DocScientia p. 44Resultant or net force Fnet 64. Determining theresultant vector: Trignometry to Scale diagram;231 Scale diagram; calculate tailhead to thetail to tail components (parallellogram)DocScientia p. 44 65. Head to tailTail to tailDocScientia p. 44 66. = 120100 N140 NDocScientia p. 44 67. Head to tail method Scale1 cm:20 N1 Axes1 vector R = 6,3 cm(from origin)= 126 N2 New axesF = 100 N= 5 cm120 to the L 442 vector 1203 Join tail of 1to head of 2F = 140 N = 7 cm= resultantDocScientia p. 45 68. Tail to tail method Scale1 cm:20 N1 Axes1 vector from originSame axes2 Measure 1202 vector from origin F = 100 NR = 6,3 cmParallellogram = 5 cm = 126 N3 Diagonal from originNo vector headstouch44Arrowhead4 Measure length - NMeasure direction 120 F = 140 N = 7 cmDocScientia p. 46 69. Rough free body1 diagram - no scaleDraw all x and ycomponents, use trig2 to calculate each ofthese componentsAdd all x componentsF = 100 N R = 126 N3 and y componentsCalculateUse pythagoras tocalculate R.Use tan to4 calculate angle(with regards to x-120F = 140 Naxis) DocScientia p. 46 70. Newtons laws of motion 71. 1An object will stay at rest or continue tomove at a constant speed in a straightline (at a constant velocity), unlessacted upon by an external net force. Professor Mac Spock explainsDocScientia p 59Newtons first law of motion/Law of inertia 72. The resistance of an object to achange in its state of motion orrest. Because of inertia objectstend to remain at rest or continue atuniform velocity.DocScientia p 60Inertia 73. Not a force characteristic ofmatter Anything with mass has inertia Mass is a measure of inertia Greater mass = greater inertiaDocScientia p 60 74. In a frictionless system: Ball reaches same height as where the motion starts, even when the slope is reduced. Loss in height is due to friction. The ball would continue to roll as long as thereDocScientia p 60 is no friction. 75. Net force is not necessary for continuous constantmotion in a straight line it is needed to stop anobject.DocScientia p 60 76. Protect against suddenchanges in motion.According to Newtonsfirst law, a person willcontinue to move until Seatbelt safetysomething stops them.DocScientia p 60 77. 2If a net force acts on an object, theobject will accelerate in the direction ofthe net force.Acceleration is directly proportional tonet force and inversely proportional tomass. Prof Mac Second LawFnet = maDocScientia p 66Newtons second law of motion 78. 3If object A exerts a force on object B,object B exerts an equal but oppositeforce on object B.12 3DocScientia p 88 Newtons second law of motion 79. Newtons law ofuniversal gravitation 80. A force of gravitational attraction exists between any two objects in the universe that have mass. This force of attraction is directly proportional to the product of the masses of the objects and inversely proportional to the squared distance between their centres of gravity.DocScientia p 95 Law of universal gravitation 81. rm1 F1 F2m2 F = G m1m2 2rDocScientia p 96 82. Universal gravitational constant. F = G m1m226,67x10 2r-11 -2 Nm kg On the information sheetDocScientia p 97 83. Mass WeightDefinition Mass =Force with which the earth or amount of another planet attracts an matter. object. Depends on the mass and radius.Scalar/ScalarVectorVectorFormulaFg = mgUnit kgNewton (N)DocScientia p 97 84. weightlessness Weight is experienced indirectly due to icalgravity. echanof m ity. t re sultra v ad irec isti ng g It issre sWeightlessnessfo rce is whengravitational forceis exerted on an object orperson. The other mechanical forces that cause the feeling the feeling of DocScientia p 98 weight are absent 85. Gravitational force surrounds everything that has mass.Gg Gravitational acceleration decreases as the distance increases.Gravitational acceleration (g) = 9,8 ms-2 Weight = attractive force of the earth on any object.Gravitational force surrounds everythingthat has mass. According to Newton: thegravitational attraction between the earthand the object.DocScientia p 98 86. GgIf one object is a planetm and the other is anobjectthe gravitationalattraction force is the rweight.The objects mass is m, Mthe planets mass is Mand the distance (radiusof the planet) is r.F = G mM mg = G mM g = G M 2 2 2r rRDocScientia p 98 87. All theory is taken from DocScientia text-and workbook book 1, grade 11Slide 1 recruitingcycle.comSlide 2 womensquest.comSlide 23 cairoo softwareSlide 32 istockphoto.comSlide 33 visualphotos.com Slide 66a dreamstime.comSlide 66b langabi.nameSlide 70 digimars.netSlide 71 TedEd on YouTube 88. Slide 75 cairoo softwareSlide 77 fictionhealth.com Slide 80 fisica.cab.cnea.gov.ar