Day 35: Average Velocity as Slope

Imag1510

Rather than introduce an equation for average velocity (v_avg = displacement/time) — which can get confusing for some kids when there are multiple segments of CV and they literally average up velocities — I decided to just go with a graphical definition (slope of position-time between the two points in question).?? In the picture, the dotted green line represents the displacement for the the whole trip and its slope is the average velocity for the whole trip. Hopefully this will ease confusion, make another link to graphs, and pay off later when we get to constant acceleration.

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About Frank Noschese

HS Physics Teacher constantly questioning my teaching.

One response to “Day 35: Average Velocity as Slope”

  1. mr bombastic says :

    It seems like you are avoiding givng a meaningful definition for average velocity. I very much like a graphical approach, but not as a crutch that allows students to succesfully compute average velocitiy when they have serious misconceptions about its meaning.I think you pretty much have to have the talk about the difference between "average velocity" and "averaging velocities". It can be an amusing discussion. Starting velocity was 80 mph and ending was 20 mph – guess the average velocity. Wrong it was 11 mph – how is that possible?

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