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Chapter 2 Legacy. Graphical Analysis of Motion. Describing Motion. First, it must be remembered that there are 3 different descriptions for motion Constant position (at rest) Constant velocity Constant acceleration. At Rest.
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Chapter 2 Legacy Graphical Analysis of Motion
Describing Motion • First, it must be remembered that there are 3 different descriptions for motion • Constant position (at rest) • Constant velocity • Constant acceleration
At Rest • For constant position or at rest, the velocity and acceleration are both 0 because the object is not moving. Position is a horizontal line because there is no change in position.
Constant Velocity • For constant velocity the acceleration is zero because the object is not accelerating. The velocity, being constant, is represented by a horizontal line. The position is then a non-horizontal linear graph because the object is moving.
Constant Acceleration • For constant acceleration the acceleration is a constant, obviously, so it is horizontal. The velocity then becomes linear because it is changing. The position-time graph then becomes quadratic, representing the non-constant speed of the object.
Degrees • Something that may help is thinking of DT, VT, and AT in terms of polynomials • The degree of a polynomial is basically a number that refers to its shape • 0- constant (horizontal) • 1- linear • 2- quadratic • 3- cubic
So for an object at rest all 3 graphs would have a degree of zero because they are horizontal • For constant velocity, velocity would be 0 and position would become 1 • For constant acceleration, acceleration would be 0, velocity would become 1, making position quadratic with a degree of 2 • For any of these quantities, each quantity below it increases by one degree from the degree of the initial quantity
Area & Slope • One more thing to know is that the slope of each graph is equal to the value of the quantity above it (slope of VT = acceleration), while the area under a graph is equal to the value of the quantity preceding it (area under VT = position). It’s always helpful to keep this in mind.