Motion Graphs Lecture 3

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Motion Graphs Lecture 3
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Video14. Bill Nye Motion
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Motion Graphs

• Motion graphs are an important tool used to show
  the relationships between position, speed, and
  time.
• Its an easy way to see how speed or position
  changes over time
• These types of graphs are called kinematic
  graphs.
• There are two types
• Position vs. Time graphs
• Speed vs. Time Graphs

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Video15. Graphing Motion
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Position Vs. Time

• Used to show an objects position at a given
  time.
• Position on y-axis
• Time on x-axis

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You Try It Graphing Position Vs. Time

• Suppose you are helping a friend who is training
  for a track meet.
• She wants to know if she is running at constant
  speed.
• You mark the track in 50-meter increments and
  measure her time at each position during a
  practice run.
• Create a position-time graph using her data.

Time (s) Position (m)
0 0
10 50
20 100
30 150
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You Try It Graphing Position Vs. Time

• When youve plotted all 4 points, you should get
  a graph that looks like this
• What would her speed be?
• Choose any point, divide distance (position)
  over time

Time (s) Position (m)
0 0
10 50
20 100
30 150
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You Try It Graphing Position Vs. Time

• What would her speed be?
• 50m/10s 5 m/s
• 100m/20s 5 m/s
• Notice that this is a straight line - why??
• She is moving at a constant speed - neither
  slowing down nor accelerating

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You Try It Graphing Position Vs. Time 2

• Graph the motion of this car.
• Graph the points (0,0), (1, 10), (2, 20), (3,
  30), (4, 40), (5, 50).
• Your graph should look like this
• What is this cars velocity?
• A constant 10 m/s

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Video16. Position vs Time
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What does slope have to do with it?

• Slope is the ratio of the rise (y-axis) to the
  run (x-axis) of a line on a graph.
• A bigger slope means a steeper line which means a
  faster speed.

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• Steeper Line Faster Speed

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Steeper Line Faster Speed
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Negative Slopes

• What does this graph mean???
• And this one?
• They show an object that is slowing down - or
  decelerating.
• The first graph is slowly decelerating, while the
  second graph is quickly decelerating.

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Basically
You might want to draw thisgraph in your Motion
Math Little book
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This is another really good graph to draw in
yourmotion math little book
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Video 17. Distance, Velocity Acceleration
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Position Vs. Time - Changing Velocity

• Now consider a car that has a changing velocity.
• It is not moving at a constant rate, but getting
  faster by the second.
• What would this graph look like?
• You try it first

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Does your graph look like this? Be sure you have
this one drawn
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You Try It GrAPHING Position Vs. Time 3

• What would the graph look like for a car that
  traveled 10 m in the 1st second, 15 m by the 2nd
  second, 25 by the 3rd second, and 40 m by the
  4th second?

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Predict What does THIS GRAPH show?
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• This graph is for a car moving with a constant
  velocity of 5 m/s for 5 seconds, stopping
  abruptly, and then remaining at rest for 5
  seconds.
• The straight line means its position is NOT
  changing.

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Speed Vs. Time

• Used to show an objects speed at a given time.
• Speed on y-axis
• Time on x-axis

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Speed Vs. Time - Constant Speed

• This graph shows the speed versus time for a ball
  rolling at constant speed on a level floor.
• On a speed vs. time graph, constant speed is
  shown with a straight horizontal line.
• If you look at the speed on the y-axis, you see
  that the ball is moving at 1 m/s for the entire
  10 seconds.

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Speed Vs. Time - Constant Speed

• Compare this speed-time graph to the
  position-time graph for the ball.
• Both of the graphs show the exact same motion,
  even though they look different.
• If you calculate the slope of the lower graph,
  you will find that it is still 1 m/s.

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You Try It Graphing Speed Position Vs. Time

• Maria walks at a constant speed of 6 m/s for 5
  seconds.
• Then, she runs at a constant speed of 10 m/s for
  5 seconds.
• Create a speed-time graph using her data.

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Speed Vs. Time - Changing Speed

• As we know, most objects dont move at a constant
  speed.
• If a speed vs. time graph slopes up, then the
  speed is increasing.
• If it slopes down, then the speed is decreasing.
• If the graph is horizontal, then the object is
  moving at a constant speed.YOU MAY WANT TO DRAW
  THESE GRAPHS TOO!

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Putting it All Together

• Which runner won the race?
• Albert won the race. He reached 100 meters first.
• Which runner stopped for a rest?
• Charlie stopped for a rest at 50m.
• How long did he stop for?
• Charlie stopped for 5 seconds. (13-8)

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Putting it All Together

• 4. How long did Bob take to complete the race?
• Bob finished the race in 14 seconds
• 5. Calculate Albert's average speed.
• Speed distance/time
• Speed 100m/12s
• Alberts Speed 8.3 m/s

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Video 18. PUTTING IT ALL TOGETHER