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Position vs. Time Graphs

Shape and slopeof lines on the

graph--give

meaning.

For Position vs.Time, we can

interpret the

velocity.

constant, rightward (+) velocity- say of +10 m/s.

Result: motion described as a constant, positive

velocity results in a line of constant and positive

slope when plotted as a position-time graph.

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Accelerating Motion

rightward (+), changing velocity- that is, a car that ismoving rightward but speeding up or accelerating.

Result: a motion described as a changing,

positive velocity results in a line of

changing and positive slope when plotted

as a position-time graph. (QUADRATIC)

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Review

Constant Velocity

Positive Velocity

Positive Velocity

Changing Velocity

(acceleration)

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Importance of SlopeP vs.

t Remember slope of a line?

Slope reveals info about velocity

As the slope goes, so goes the velocity

Constant Velocity=Constant Slope (straightline)

Velocity changes=slope changes (curvedline)

Velocity is positive = slope is positive(moving upwards and to the right)

Steeper slope, faster velocity

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Which Has a Greater

Velocity?

Slow, Rightward(+)

Constant Velocity

Fast, Rightward(+)

Constant Velocity

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Negative Slope

Slow, Leftward(-)

Constant Velocity

Fast, Leftward(-)

Constant Velocity

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Back to Curved Slope Lines

Curved Lines =changing slope =acceleration

Starts with a smallslope

Ends with a largeslope

What does this say

about its velocity inthe beginning andthe end?

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Example:

If Paul walks three meters at 1 m/s, then stops

and walks back at 1.5 m/s, what would the P

vs. T graph look like?

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Velocity vs. Time Graph

Note that a motion

described as a

constant, positive

velocity results in aline of zero slope (a

horizontal line has

zero slope

Slope for V vs. T =acceleration

constant, rightward (+) velocity - say of

+10 m/s

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Accelerated Motion

A car that is moving

rightward but

speeding up or

accelerating.

The slope of the line

is positive,

corresponding to the

positive acceleration

rightward (+), changing velocity

http://www.physicsclassroom.com/class/1dkin/U1L1e.cfmhttp://www.physicsclassroom.com/class/1dkin/U1L1e.cfm

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Review

Positive Velocity

Zero Acceleration

Positive Velocity

Positive Acceleration

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Meaning of Slope V vs. t

Slope of a velocity-time graph reveals info

about the acceleration.

Acceleration, zero = straight line (zero

slope) Positive acceleration, positive slope

(upward line)

Negative acceleration, negative slope

(downward sloping line)

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Positive and Negative

Positive direction, if it lies above zero.

Negative direction if it lies below zero.

Can be speeding up or slowing down.

If it crosses over zero on x-axis, it changesdirection.

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Example

If Paul walks three meters at 1 m/s, then

stops and walks back at 1.5 m/s, what would

the V vs. T graph look like?

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Speeding up or Slowing down? Speeding up if the

magnitude (numericalvalue) of velocity isgetting larger.

From 3 m/s to 9 m/sor from -3 m/s to -9m/s.

The number itself iskey, not the sign ordirection.

Speed up: movingaway from 0-velocityline

Slowing down: movingtowards the 0-velocityline.