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For more information, please see full course syllabus of Physical Science
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Lecture Comments (2)

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Post by Linda Volti on February 15, 2014

Could you re-clarify velocity please. I thought velocity was displacement/time, so that in the turtle example it would be 5 metres per 15 seconds east - or 1/3 metre per second east.

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Post by Dania Aljeilani on October 17, 2013

The practice questions are not related to motion.

Motion

  • Distance is the total distance traveled.
  • Displacement is the distance from the start point to the end point.
  • Speed is distance/time. Velocity is speed and direction of the motion.
  • Instantaneous speed is the speed at a specific moment. Average speed is the total distance divided by the total time.
  • A distance-time graph shows how the distance of a moving object changes over time.
    • A straight line means the object is moving at a constant speed.
    • The steeper the graph, the greater the speed.
    • A horizontal line means the object is stopped.
  • Acceleration occurs when a change in velocity occurs (speed or direction).
  • ACCELERATION EQUATION - a=(vf – vi) / (tf – ti)
  • A speed - time graph shows us how the speed of a moving object changes with time.
    • The steeper the graph, the greater the acceleration.
    • A horizontal line means the object is moving at a constant speed.
    • A downward sloping line means the object is slowing down.

Motion

In what situation would the displacement of an object in motion be zero?
When the object starts and stops its motion in the exact same place.
How is speed different from velocity?
Mathematically, they are the same, but velocity includes the DIRECTION of the object in motion.
What information does the slope of a distance-time graph give you?
The speed
What information does the slope of a speed-time graph give you?
The acceleration
What does a curved line on a distance-time graph indicate?
The rate of speed is changing
What does a steeper line on a distance-time graph indicate?
An object moving at a higher speed will have a steeper line.
When the acceleration of an object is calculated and the answer is a negative number, what does that tell you?
That the object has negative acceleration, which means it is slowing down.
What does a horizontal line (across from side to side) on a distance-time graph indicate?
That the object is not moving (covers no distance)
What does a horizontal line (across from side to side) on a speed-time graph indicate?
That the object is moving at a constant speed
What is the acceleration of a car that is traveling at a rate of 2m/s and continues at that rate as it completes a turn towards the West?
Acceleration = 0m/s2 West - The only change is the direction of the moving object

*These practice questions are only helpful when you work on them offline on a piece of paper and then use the solution steps function to check your answer.

Answer

Motion

Lecture Slides are screen-captured images of important points in the lecture. Students can download and print out these lecture slide images to do practice problems as well as take notes while watching the lecture.

  • Intro 0:00
  • Distance vs. Displacement 0:04
    • Distance
    • Displacement
  • Speed 4:47
    • Speed
    • Instantaneous Speed
    • Average Speed
    • Velocity
  • Distance-Time Graphs 8:21
    • Distance-Time Graphs
  • Acceleration 13:38
    • Acceleration Definition
    • Acceleration Equation
    • Positive Acceleration
    • Negative Acceleration
  • Speed-Time Graphs 20:56
    • Speed-Time Graphs
  • Example 1: Displacement, Distance, and Average Speed 25:15
  • Example 2: Velocities 28:02
  • Example 3: Acceleration 28:59
  • Example 4: Distance and Time 30:19
  • Example 5: Speed and Time 34:08