Describing Motion with Diagrams

Describing Motion with Diagrams Ticker Tape Diagrams A long tape attached to a moving object and threaded through a device that places a tick upon the tape at regular intervals of time – leaving a trails of dots

Ticker Tape Diagrams The distance between dots represents the object’s change in position during that time interval small distance – slow moving Even distances = constant velocity large distance – fast moving

Ticker Tape Diagram A changing distance between dots indicates a changing velocity – acceleration

Graphing Motion

Graphing Motion ZERO MOTION The object is at rest Position-time graph (x vs t) position of an object remains constant over time Velocity-time graph (v vs t) object is not moving, it has 0 velocity Acceleration-time graph (a vs t) If the object’s velocity is not changing, its acceleration is 0 The acceleration is zero because velocity is not changing not because the velocity is zero Sketch above graphs

Graphing Motion Uniform Motion – Constant Velocity x vs t graph as time increases so does the position *slope of a x vs t graph = velocity v vs t graph velocity remains constant over time *this should reflect the value of the slope of the x vs t graph a vs t graph velocity is not changing, acceleration is 0 *slope of a v vs t graph is acceleration Steeper slope – faster velocity Shallow slope – slower velocity

Graphing Motion Uniform Accelerated Motion x vs t graph – position is increasing exponentially with time (acceleration) v vs t graph – velocity is increasing with time (acceleration) a vs t graph – acceleration is constant. The value of a is equal to the slope of the v vs t graph Acceleration will always be a horizontal line

Tangent Lines t On a position vs. time graph: SLOPE VELOCITY Positive Position time graph x Tangent Lines t On a position vs. time graph: SLOPE VELOCITY Positive Negative Zero SLOPE SPEED Steep Fast Gentle Slow Flat Zero

Increasing & Decreasing Position time graph Increasing & Decreasing t x Increasing Decreasing On a position vs. time graph: Increasing means moving forward (positive direction). Decreasing means moving backwards (negative direction).

Concavity On a position vs. time graph: Position time graph t x Concavity On a position vs. time graph: Concave up means positive acceleration. Concave down means negative acceleration.

Describe the motion This object is moving in the positive direction and accelerating in the positive direction (speeding up). This object is moving in the negative direction and accelerating in the negative direction (speeding up). This object is moving in the negative direction and accelerating in the positive direction (slowing down).

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Area under a v vs t graph The area of a v vs t graph is displacement