Mechanics the study of how objects move and respond to external forces Kinematics study of motion with no concern for the cause Motion Perceiving motion is instinctive your eyes pay more attention to moving objects ID: 783316
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Slide1
Unit 2
1
Dimensional
Motion
Slide2Mechanics – the study of how objects move and respond to external forces
Kinematics – study of motion with no concern for the cause
Motion
Slide3Perceiving motion is instinctive
—
your eyes pay more attention to moving objects than to stationary ones. Movement is all around
you.Movement travels in many directions, such as the straight-line path of a bowling ball in a lane’s gutter, the curved path of a tether ball, the spiral of a falling kite, and the swirls of water circling a drain.When an object is in motion, its position changes. Its position can change along the path of a straight line, a circle, an arc, or a back-and-forth vibration.Motion
Slide4A description of motion relates to place and time. You must be able to answer the questions of where and when an object is positioned to describe its motion.
In the figure below, the car has moved from point A to point B in a specific time period.
Motion
Slide5Particle Model
Slide6Relative Motion
Slide7Relative Motion
Slide8Relative Motion
Slide9Relative Motion
Slide10Relative Motion
Slide11Relative Motion
Slide12A) What is your speed relative to the ground?
100 km/h
B) What is your speed relative to the seat you are sitting in?
0 km/hC) What is the speed of the fly relative to you? 0 km/hRelative Motion
Slide13Relative Motion
Slide14A coordinate system tells you the location of the zero point of the variable you are studying and the direction in which the values of the variable increase.
The origin is the point at which both variables have the value zero.
Coordinate System
Slide15In the example of the runner, the origin, represented by the zero end of the measuring tape, could be placed 5 m to the left of the tree.
The motion is in a straight line, thus, your measuring tape should lie along that straight line. The straight line is an axis of the coordinate system.
Coordinate System
Slide16You can indicate how far away an object is from the origin at a particular time on the simplified motion diagram by drawing an arrow from the origin to the point representing the object, as shown in the figure.
Coordinate System
Slide17Coordinate System – define
an
origin and a positive directionMust remain consistentIn one
dimensionTypically to the right is positive, left is
negativeCoordinate System
Slide18Coordinate System
Position – a reference to the coordinate system
Slide19Slide20Coordinate System
Slide21Coordinate System
Slide22Vectors and Scalars
Slide23Vectors and Scalars
Slide24Speed and Velocity-
Speed is a scalar quantity. It only contains magnitude (number). Ex. 50 mph
Velocity is the vector quantity. It contains both magnitude and direction. Ex. 50 mph N
Vectors and Scalars
Slide25Distance and Displacement
Distance is the total length traveled from beginning to end. It is a scalar quantity (magnitude only). Ex. 14 m
Displacement is the position in reference to the origin. It is a vector quantity and includes both magnitude and direction. Ex. 14 m N
Vectors and Scalars
Slide26Distance is 84.5 m, displacement is 84.5 m E.
Vectors and Scalars
Slide27Distance traveled is 84. 5 m, displacement is 24.5 m E.
Vectors and Scalars
Slide28Velocity
Slide29Slide30Slide31Slide32Slide33Slide34Slide35Average velocity
Defined as the total distance over the total time
Used when determining ETA by GPS; over long trips
Velocity
Slide36Instantaneous Velocity
Velocity at any instant in time.
Measured by your speedometer in your carUsed by police to issue tickets
Velocity
Slide37Constant Velocity
Velocity that is unchanging
Speed of sound, speed of light, cruise control
Velocity
Slide38Defined as changing velocity; either positive or negative
Since acceleration is a vector quantity either a change in the magnitude or the direction will cause acceleration
Acceleration can be either positive or negative
Deceleration is a special case of acceleration= negative acceleration
An object turning or going in a circle is accelerating even if the speed is constant.
Acceleration