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Published byMervyn Gregory Modified over 9 years ago
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Linear Kinematics Describing Objects in Motion
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Define Motion: »Motion is...
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Define Motion: »Motion is a change in position over a period of time. Space and Time
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Types of Motion l Linear Motion (translation) »all points on the body move –the same distance –in the same direction –at the same time »Rectilinear Translation: straight lineRectilinear Translation –figure skater gliding across the ice »Curvilinear Motion: curved lineCurvilinear Motion –free-fall in sky-diving
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Types of Motion l Linear Motion (translation) l Angular Motion (rotation) »all points on the body move –through the same angle »Whole body rotationWhole body rotation –giant swing, pirouette »Segment rotation –flexion, abduction, yada yada yada ….
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Types of Motion l Linear Motion (translation) l Angular Motion (rotation) l General Motion »combines angular and linear motion »most common type of human movement –pedaling a bike –walking –drawing a straight line
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Linear Kinematics l Description of Linear Motion »how far? »What direction? »How fast? »Speeding up, slowing down?
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Position l Identifying location in space »at the start of movement? »At the end of movement? »At a specific time in the midst of movement? l Use a fixed reference point »1 dimension –starting line, finish line »2 dimension –Bloomington-Normal: north, east, south, west –(goal line, sideline), (0,0), Cartesian coordinate system
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Recall: Vector & Scalar Quantities l Scalar: Fully defined by magnitude »mass l Vector: Definition requires magnitude and direction »force
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Distance and Displacement l Measuring change in position »component of motion l Football player: »receives kickoff at 5 yard line, 15 yards from the left sideline »runs it back, deking defenders over a twisted 48 yard path, to 35 yard line, 5 yards from the left sideline
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Distance and Displacement l Distance »length of path traveled: 48 yards l Displacement »straight line distance in a specified direction »y direction: y final - y initial »x direction: x final - x initial
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Distance and Displacement l Resultant Displacement »length of path traveled in a straight line from initial position to final position –y direction: y final - y initial –x direction: x final - x initial Components of resultant displacement R 2 = ( x) 2 + ( y) 2
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Distance and Displacement l Resultant Displacement »length of path traveled in a straight line from initial position to final position –y direction: y final - y initial –x direction: x final - x initial Components of resultant displacement R 2 = ( x) 2 + ( y) 2 = arctan (opposite / adjacent)
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Speed and Velocity l Measuring rate of change in position »how fast the body is moving l speed »scalar quantity –how fast Speed = time distance
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Speed and Velocity l Measuring rate of change in position »how fast the body is moving l speed »scalar quantity –how fast Speed = time distance meters seconds
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Examples l Who is the faster runner: »Michael Johnson –100m in10.09s –200m in 19.32s (world record) –300m in 31.56 s –400m in 43.39s (world record) »Donovan Bailey (Maurice Greene)Donovan Bailey –50m in 5.56 s (world record) »http://www.runnersweb.com/running/fastestm.html
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Quiz What 1970’s rock band is named after a gym teacher?
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Instantaneous Speed l We have calculated average speed »distance by time to cover that distance l Maximum speed in a race? »Make the time interval very small » 0.01 second or shorter
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Speed and Velocity l Measuring rate of change in position »how fast the body is moving l speed l velocity »vector quantity –how fast in a specified direction velocity = time displacement m s
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Example l Swimmer »100 m race in 50 m pool »24s and 25s splits l Calculate velocities & speeds » first length, second length » total race (lap)
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Example l Football player: »receives kickoff at 5 yard line, 15 yards from the left sideline »runs it back, deking defenders over a twisted 48 yard path, to 35 yard line, 5 yards from the left sideline l time is 6 seconds l Calculate velocities & speeds » forward, side to side, resultant
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Use speed to calculate time l Running at 3 m/s l How long to cover 2 m?
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Projectile Motion Click here to go to a site showing the predictability of projectile motion (applied kinematic equations) Or here for a site on the high jump.
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Use these concepts, make yourself $$$$
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Quiz If a body is traveling in the + direction and it undergoes a – acceleration, the body will ____________________. If a body is traveling in the – direction and it undergoes a + acceleration, the body will ___________________. Speed up or slow down
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Acceleration l Quantifying change of motion »speeding up or slowing down »rate of change of velocity Acceleration = velocity time v f - v i t f - t i =
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Soft landing from 60 cm
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80% 1RM BP, Narrow vs Wide Grip
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