KIN 365 1st Edition Exam 4 Study Guide I Fluid Forces A pg 115 116 manual ch 9 hardback B Drag Forces 1 parallel component of dynamic fluid force acting in opposite direction of system in motion with respect to fluid 2 tends to resist motion of system C Lift Forces 1 perpendicular component of dynamic fluid force acting in any direction perpendicular to system in motion with respect to fluid 2 changes direction of system in motion D relative motion 1 relative motion between object and fluid force a ex headwind tailwind side wind 2 important factor is how fast object is going in relation to fluid force not in relation to ground E Drag force 1 deceleration of motion 2 parallel component of dynamic fluid force 3 acts in opposite direction of system motion with respect to fluid 4 tends to resist the motion of the system through fluid F Fluid drag force These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute 1 aka fluid resistance 2 force in opposite direction of motion of object a aerodynamic air b hydrodynamic water 3 want to go through air water but something impeding ability of the acceleration of object G Two Types of Drag Force 1 skin friction a aka surface drag b boundary layer 1 region of relative motion between adjacent layers of fluid particles c layer rubbing friction 1 H2O vs air 2 more friction in water because water is heavier than air d affected by three factors 1 velocity of flow a relative to air b faster you move more friction 2 amount of SA oriented parallel to flow a where all rubbing occurs b greater area more friction 3 roughness of surface a coefficient of friction b more roughness more friction 2 profile drag a aka pressure or form drag b main type of drag force acting on us and projections anything we throw c turbulent flow 1 motion around object is turbulent not smooth 2 other friction forces besides friction present 3 goal is to minimize turbulence streamlining d laminar and turbulent flow 1 laminar flow a smooth b no turbulence c only friction drag present 2 turbulent flow a not smooth b very turbulent c ex what we feel when passing an 18 wheeler i II Four Factors That profile drag present in addition to friction drag Affect Drag A Coefficient of Drag Cd 1 how streamline object is 2 higher Cd more drag force slows 3 examples a parachute slows you down b fish swims fast through water c old cars vs new cars d leisure vs Olympic bike helmet B Area A 1 frontal area 2 area facing flow 3 larger area more drag force C Fluid Density p 1 everything to do with altitude 2 more dense fluid more drag a more drag at sea level b less drag at higher altitudes c more home runs in Denver D Flow Velocity v 1 most important factor 2 little change in relative motion of object to fluid big difference in drag 3 faster you go more drag 4 relative motion between object and fluid a how fast fluid is going with respect to object b how fast object is going with respect to fluid E Drag Force 1 2 Cd A p v 2 III Lift Force A upward downward motion B perpendicular component of dynamic fluid force C can act in any direction that is perpendicular to system motion with respect to fluid D tends to change the direction of systems motion through fluid IV Factors Affecting Lift A Area A 1 angle of attack 2 orientation of object that is angled perpendicular to fluid flow 3 ex a smaller angle glider b larger angles large plane leaves c large angle more lift force to point V Lift Drag ratio A ratio that expresses the relationship of the amount of lift to amount of drag at angle of attack B ratio favoring drag will reach stall angle C Stall angle 1 flight no longer possible VI Linear Movement and Acceleration A Newton s First Law 1 body at rest stays at rest 2 body in motion stays in motion unless acted on by outside force 3 change in motion is caused by an outside force B Newton s Second Law 1 acceleration of a system directly proportions to sum of forces net force acting upon it and inversely proportional to mass 2 acceleration sum force mass 3 degree an object at some mass will be accelerated is a directly proportional to amount of force C b inversely proportional to objects mass observed change in state of motion is acceleration VII Acceleration A change in magnitude and or direction of velocity vector with respect to time measured in Newtons N B one Newton force needed for object of one kilogram to be accelerated by one mile per second C Velocity 1 vector rate of motion 2 has both magnitude and direction 3 rate of motion in specific direction calculated with the following equation a v d tf ti b velocity displacement divided by change in time D Linear Displacement Distance 1 change in position of object 2 position final position initial 3 in a straight line 4 measured in linear units miles kilometers 5 d position final position initial E object or system may not have same rate of motion throughout movement 1 rate of motion may not be necessarily a constant through motion 2 can calculate a average velocity peak velocity rate of motion b instantaneous velocity or rate of motion F variable velocity 1 average velocity total distance time 2 instantaneous or peak velocity VIII Linear Momentum A another factor that affects outcome of interactions between two bodies is momentum B momentum 1 mechanical quantity that is particularly important in situations involving collisions 2 quantity of motion 3 mass velocity 4 kg m s 5 vector quantity C if something is moving fast or is big 1 has a lot of momentum 2 takes larger or prolonged force to bring it to a stop D an object at rest zero momentum 1 no change in object s momentum will occur without application of externally applied force causing change in velocity of object E force momentum relationship 1 F mv2 mv1 time IX Aerodynamic Lift A lift will always be perpendicular to relative flow direction B lift does not always have to be upward C ex ceiling fan 1 leading edges tilted up air down 2 leading edges tilted down air up X Force of Lift A lift force 1 2 Cl A p v 2 B most important factor is flow velocity C little change in relative motion of object to fluid will create big difference in lift D Coefficient of Lift 1 Cl 2 expresses the capability of a particular object to create lift 3 coefficient of lift is affected by the shape texture orientation relative to fluid flow a higher Cl more force XI Linear Acceleration A now that we know how to calculate the