1-D Kinematics: Graphing Velocity

1-D Kinematics: Graphing Velocity

Interpreting Motion from Velocity Graphs

Velocity vs Time Graphs

• constant positive slope = acceleration

• no slope = moving at a constant rate

• constant negative slope = slowing down

• changing slope = increasing or decreasing acceleration

Calculating Acceleration from V vs t Graphs

• Slope of V vs t Graph = Acceleration

• Slope (m) = Rise / Run = (y2-y1)/(x2-x1)

• What would be the acceleration of this object?

• Pick 2 coordinate sets.

• (x1,y1)(x2,y2).....(0,0)(4,8)

• Plug into slope equation....

• m = (8-0)/(4-0) = 8/4 = 2 m/s/s (units for V on graph are wrong)

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What is the acceleration of the object that is speeding up? (include units)

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What is the acceleration of the object that is slowing down? (include units in your answer)

What if graph crosses the x axis into negative territory???

• the sign on velocity just represents direction

• (+) velocity = object traveling right or up.

• (-) velocity = object traveling left or down.

• so if a Velocity vs time graph crosses the X axis it just means the object is changing direction.

Determine displacement from a Velocity vs time Graph

• Displacement on a Velocity vs time Graph = AREA UNDER THE GRAPH

• Divide up area under the graph into rectangles and triangles.

• Find area of each and add together.

• Area of triangle = 1/2(b*h)

• Area of rectangle = l*w

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What is the distance travelled by the object that made this graph? (include units in your answer)

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What is the distance travelled by the object that made this graph? (include units in your answer)

What if its a CURVE???

• You need calculus to solve!

• This is a CP class so we will stick to constant slopes!

That's the END of Section 1

(Describing Motion using Graphs)