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Re: Free Body Diagram



> searching for
> the words that my high school class will understand and will convince
them (and me) why one is correct and the other incorrect.

The idea that the vertical acceleration goes to zero is actually a variant
of the common misconception that students have. They think that the
acceleration goes to zero when a ball is thrown up and reaches it's peak
where the velocity is zero. Students may wish to hang onto that explanation
as the misconception is fairly resistant to change.

VEEEEERY resistant to change!!!!!!

But, long before the idea of a free body diagram is approached, the
students should have worked MANY velocity vs. time graph type
problems.

Most HS students can reach the point of correctly graphing the
vertical velocity of an object that is thrown upwards into the air.

Once they have drawn this graph - they STILL will need time to beat
their head against the idea that:
the slope is constant
and that
the slope is the acceleration
so

the acceleration is NOT zero as the graph crosses the x-axis.

Just because we can recite the correct words, does not guarantee that
we know what we are talking about.

Velocity graphs will sink in better than words for some of the more
visual thinkers in your classes.

This posting is the position of the writer, not that of SUNY-BSC, NAU or the AAPT.