Distance/speed problem

  1. A horse canters away from its trainer in a straight line, moving 140 m away in 14.0 s. It then turns abruptly and gallops halfway back in 4.3 s.

    (a) Calculate its average speed. (m/s)

    (b) Calculate its average velocity for the entire trip, using "away from the trainer" as the positive direction. (m/s)

    To start, I have drawn a graph to represent this situation, with time on the x-axis and distance on the y-axis. 1) I don't know how average speed and average velocity are different (since I thought they were both how fast something is going, or the slope of the graph), and 2) I don't know how to find the derivative of the graph since it is not linear and I am given no additional information about the equation of the graph.

    Maybe I am thinking way too far into this. I am new to physics, but I've had lots of math.

    Thanks in advance for the help.

  2. jcsd
  3. Well if you know anything about vectors and scalars, then the difference should be easy to realize that speed is a scalar value and velocity is a vector value.

    average speed = total distance covered / time

    average velocity = total displacement / time
  4. Thanks for the explanation. Yep, I've never had any college or high school physics before so I had never heard about that difference.
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