Exam 2 Review PDF

1 Exam 2 Review The information below is a summary only of the lecture material that will be covered in the second exam. You will need to consult your notes, the power point slides, and your text book (readings as assigned in lecture, but also as a reso...

1 Exam 2 Review The information below is a summary only of the lecture material that will be covered in the second exam. You will need to consult your notes, the power point slides, and your text book (readings as assigned in lecture, but also as a resource to help clarify some of the other lecture material) in preparing for this exam. All formulas that may be used are bold-faced in this review (formula sheet will be provided).  Lecture: Angular Kinematics Text book: pgs 154-163 o Relative vs. Absolute angle o Angular distance ( phi) vs Angular Displacement (theta ): same as linear  Counter-clockwise positive, clockwise negative  Right-hand-thumb rule o 3 measurements (degrees, revolutions, rads) o # of radians = d/r [arc length/radius] or d = θr o The greater the distance of a given point on a rotating body from the axis of rotation, the greater the linear displacement of that point (assuming the same angular displacement) o Angular velocity = angular displacement/change in time (ω = θ/t) o tangential velocity (vT) vT = ω x r  Tangent – line that just touches the arc created by a point on a rotating body; is perpendicular to the radius of the arc at that point.  longer vs shorter radius, ω equal for both, longer radius will have greater vT  longer vs shorter radius, vT equal for both, shorter radius will have greater ω o Angular Acceleration  α = (ωf – ωi)/t o Centripedal & Centrifugal acceleration  Lecture: Linear Kinetics (Forces) Text book, added resource: Chpt 3 o Unit of force = N(ewton) = kg m/s2 o Newton’s laws  Inertia  Acceleration  Action/reaction o Friction  Normal Force (gravity)  Friction Force  Static friction - µs = ≤ fs/Fn  Kinetic friction - µk = ≤ fk/Fn  Rolling friction o Momentum = mass velocity  This is a vector (has direction and magnitude)  2  Important in collisions o Conservation of momentum  Momentum prior to collision = momentum post collision (provided no additional external forces applied)  So, m1v1 (before) + m2v2 (before) = m1v1 (after) + m2v2 (after) o Impulse = Ft  Ft = mvf – mvi  Implications – landings, quick starts/stops, acceleration of objects/projectiles o Collisions  Elastic vs inelastic  Loss of kinetic energy in collisions  Elasticity measured by Coefficient of Restitution (e), determined by;  Composition of the object  Composition of the surface of the object  Temperature  e is calculated by  separation speed/approach speed or  √(hb/hd) (sqr rt of bounce height/drop height) o Collisions may be direct (head on) or in-direct (at an angle – more common)  In-direct – angle of incidence (before) and angle of reflection (after)  Reflection affected by  The elasticity of the object  The level of friction at the contact point  The amount of spin on the object o Pressure  P = Force/area (same force but smaller area = greater pressure)  Units  Pascals or N/m2  Implications for landings, padding, helmets, etc.  Lecture: Angular Kinetics Text book: Chpt 5 (pgs 124-130); Chpt 7 (pgs 180-186, 189-196) o Torque (off-centre or eccentric force) = F x d (perpendicular distance of force from axis of rotation) o Levers – made up of  Axis (fulcrum), Force (motive force), & Resistance (resistance force)  1st, 2nd, & 3rd class levers (ARF)  FA x F = RA x R (Force Arm x Force = Resistance Arm x Resistance)  Mechanical Advantage – for levers, MA increases as the FA increases relative to the RA (MA = FA/RA)  I.e. – The further the perpendicular distance of the Force Arm from the axis, the greater the torque that force can apply.  Furthermore, the longer the Force Arm relative to the Resistance Arm, the greater the mechanical advantage (i.e., strength) of that lever, but the trade-off is a slower linear velocity of the end of the lever (i.e., end of the limb).  3 F (muscular contraction) R (gravity) o Angular Inertia  Property of an object that resists change in angular motion  Affected by mass (m) and distribution of mass (k 2)  Greater mass  greater Ia  Mass further away from axis of rotation  greater Ia  Distribution of mass also referred to as radius of gyration (k)  k = Distance from axis of rotation to a point at which the mass of the body can theoretically be concentrated without altering the inertial characteristics of the rotating body  Moment of inertia - quantity of angular inertia (I = mk2) o Angular momentum (H)  Moment of Inertia x angular velocity (H = Ia ω, or H = mk2w)  Affected by  Mass  Distribution of mass – has the most impact on H  Angular velocity o Conservation of angular momentum - The total angular momentum of a given system remains constant in the absence of external torques  Gravity has no effect because does not create torque (eccentric force)  Implications  once athlete has left the ground, cannot add angular momentum  in order to speed up or slow down rotation, athlete must redistribute mass (lengthen or shorten k – tuck legs in, fold into pike, etc.)  ω must change to conserve angular momentum  Lecture: MPA & Kinetic Link o MPA – 3 main steps  Skill phasing/examining stereotype – generally, six phases  Principles/Key performance factors application – need to know purpose of skill  Coaching/Feedback – view skill from multiple angles, be specific, identify underlying mech. Problem, etc. o Kinetic Link – coordination of linked body segments to create force/velocity  Simultaneous – body segments move together – usually for accuracy or force  4  Sequential - body segments move in sequence  Most often with Kinetic Link/Chain, talking about sequential  Sequential velocity of segments, well-timed, build on each other  Requires (for max. velocity)  Max. # of body parts/joints/planes  Max. velocity created in each segment  Coordination of these velocities – smooth energy transformations  Direction principle – forces applied directly in line with direction of motion  Duration of Force – increase time of constant force applied to increase velocity (Ft=mvf-mvi)  Lecture: Fluid dynamics Text book, added resource: Chpt 8 o Characteristics of fluid  Laminar flow – fluid in layers, move relative to each other  turbulent flow – layers are disturbed  ease of movement through layers = viscosity (resistance to flow) o Buoyancy – tendency of object to float/rise in fluid  Archimedes principle - “Any body in a fluid will experience a buoyant force equal to the weight of the volume of the fluid that it displaces.”  Implications – denser bodies (i.e., more muscular) more likely to sink  Density = mass/volume  Center of Buoyancy - that point at which the buoyant forces are said to act  Different from C of G (superior to C of G – determines how a body “sits” in fluid) o Drag - opposing force acting on an object travelling through a fluid  Form (profile) drag, affected by  the area on which the fluid acts  Creates pressure differential  Positive at the leading surface, negative behind  Force directed from high to low  Surface drag (skin friction), affected by  Relative velocity of fluid flow  Surface area of body  Viscosity of the fluid  Roughness of the body surface  Wave drag  Effects felt only in water  High-pressure wall in front of moving body  The faster the movement, the larger the force  Theoretical square law  All other factors being equal, drag increases with the square of the relative velocity of motion  Cyclists crouching low can create a ten-fold reduction in drag  Except for wave drag, which increases with the cube of the relative velocity of motion o Lift  5  acts at right angles (perpendicular) to the relative flow  created by different pressures on opposing sides of the object (from high to low)  Also, reaction forces of fluid against object resulting from object’s force applied to fluid (Newton’s 3rd Law at work)  Bernoulli’s principle - The total energy in steady flowing fluid system is a constant along the flow path. An increase in the fluid’s speed must therefore be matched by a decrease in its pressure  Angle of attack o Magnus effect – spin on a ball causes path of ball to be curved  Curve occurs in direction of spin (low pressure)