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2D Motion

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Introduction to Motion in Two and Three Dimensions

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Position, Velocity, and Acceleration as Vectors

Kinematics Terms

Terms

Kinematics - Kinematics is concerned with describing the way in which objects move.

Displacement - An object's total change in position. If a man runs around an oval 400 meter track, stopping at the precise location he began, though he ran a distance of 400 meters, his total displacement was 0.

Dynamics - Dynamics focuses on understanding why objects move the way they do.

Reference frame - The coordinate system with respect to which motion is being described.

Speed - A measure of how fast an object is moving.

Average velocity - The time-average of the velocity function over a specified time-interval. (See formula below.)

Instantaneous velocity - The value of the velocity function at a particular instant in time. (See formula below.)

Gravitational acceleration - The graviational acceleration of objects near the earth's surface is the same for all objects regardless of mass and is given by the number g = 9.8m/s² .

Scalar-valued function - A function that outputs scalars (regular numbers). Most common functions that you are probably familiar with are scalar-valued functions.

Vector-valued function - A function that outputs vectors. This means that while the domain of the function may consist of scalars, the values in the range are all vectors.

Position function - A position function can be either scalar-valued (for motion in one dimension) or vector-valued (for motion in two or three dimensions). At each point in time its value represents the position of an object at that time.

Velocity function - This function is the time-derivative of the position function, and gives the velocity of an object at each point in time.

Acceleration function - This function is the time-derivative of the velocity function, and the second time-derivative of the position function. It gives the value of the acceleration of an object at each point in time.

Time-derivative - The time-derivative of a function is a new function whose value at each point represents the rate of change of the original function with respect to time.

Simple harmonic motion - Periodic motion that can be described by special types of position functions. Examples of simple harmonic motion include an object moving in a circle and a ball bouncing up and down on a spring.