# MOTION speed, velocity and acceleration Motion Notes— What is motion? Motion is relative Displacement vs. Distance Constant vs. Changing Motion Three.

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MOTION speed, velocity and acceleration

Motion Notes— What is motion? Motion is relative Displacement vs. Distance Constant vs. Changing Motion Three possible motions

What is Motion? Motion occurs when an object changes position The position of the object depends on your frame of reference. A frame of reference refers to the stationary background to which the object’s position is compared.

Motion is relative Motion is relative to a chosen frame of reference. You at rest at your table…are you moving? Relative to the floor? Relative to the school building? Relative to the ground? Relative to the Sun? Relative to the Galaxy? Relative to the Universe? http://www.phy.ntnu.edu.tw/java/relativeVelocity/relative Velocity.htmlhttp://www.phy.ntnu.edu.tw/java/relativeVelocity/relative Velocity.html http://www.classzone.com/books/ml_science_share/vis_ sim/mfm05_pg7_relmotion/mfm05_pg7_relmotion.htmlhttp://www.classzone.com/books/ml_science_share/vis_ sim/mfm05_pg7_relmotion/mfm05_pg7_relmotion.html

Descriptions of Motion Relative motion—motion of objects as perceived from your frame of reference Linear motion—motion of objects moving in straight lines (opposite of non-linear) Constant motion—motion of objects in mechanical equilibrium (no change in motion) Changing motion—motion of objects that are accelerating

Displacement vs. Distance Displacement is the distance and direction of an object’s final position from its initial position. Distance is the length of the path that the object travels.

Three Possible States of Motion At rest Constant velocity (same speed and direction) Acceleration (changing speed and/or direction)

Describing Motion By definition By comparison By measurements By equations By graphs

SPEED IS… HOW FAST AN OBJECT MOVES. total distance covered divided by time it takes to cover that distance Speed equation v = d/t SI unit is meters/second (or m/s) Example… 40 m/s

VELOCITY IS… SPEED IN A GIVEN DIRECTION Speed is determined by the speed equation Direction of speed is described SI unit is m/s and direction example… 40 m/s east

ACCELERATION The rate of change in velocity over a period of time. SI unit is m/s 2 example… 4.5 m/s 2 or - 4.5 m/s 2 Positive means speeding up, negative means slowing down Velocity changes in two ways –#1: a change in speed (acceleration or deceleration) –#2: a change in direction (turning)

ACCELERATION EQUATION Acceleration = final velocity – initial velocity final time – intial time a = v f - v i t f - t i

GRAPHING SPEED Two types of graphs –Distance-time graphs –Velocity-time graphs

RELATIVE MOTION WEB SITES http://www.phy.ntnu.edu.tw/java/relativeVe locity/relativeVelocity.htmlhttp://www.phy.ntnu.edu.tw/java/relativeVe locity/relativeVelocity.html http://www.physicsclassroom.com/mmedia /kinema/kinemaTOC.htmlhttp://www.physicsclassroom.com/mmedia /kinema/kinemaTOC.html http://hyperphysics.phy- astr.gsu.edu/hbase/relmot.htmlhttp://hyperphysics.phy- astr.gsu.edu/hbase/relmot.html http://www.ii.metu.edu.tr/emkodtu/met106/l ectures/motion_in_2_and_3d/page9.htmlhttp://www.ii.metu.edu.tr/emkodtu/met106/l ectures/motion_in_2_and_3d/page9.html

RELATIVE MOTION Motion relative to your perspective or frame of reference. In order to see an object in motion, you need a perspective or frame of reference, such as a stationary background, for comparison.

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