[Phys-L] Re: student difficulties with velocity as a vector?

[jlu at HEP.ANL.GOV (Jack Uretsky)]

On Sat, 29 Oct 2005, Robert Cohen wrote (in part):

> My students, by the way, score at around 25% on the FCI before
> instruction and I suspect part of the problem is their reading ability.
> For example, I believe the problem with the question I posed in my
> previous message was with interpreting the word "initial"

        Looking at your results (below), I'm inclined to agree with you.
My hunch is, that they read right over the adjective and focus on the word
velocity.  You can check this hunch quickly by requiring them to show
a calculation in arriving at an answer (which will probably change the
result).
        I base my hunch on observation of students coming to school early
and doing their homework - usually math.  The homework is often a set of
nearly identical drill problems which can be done without paying close
attention (often done while listening to a CD or other audio device).
They are simply not in the habit of careful reading, which is not needed
for such homework.  Requiring that all answers be supported helps cure
this disease, and is one ofthe benefits of the Hake type Discussion Labs.
                                Regards,
                                                Jack





> rather than
> with calculating the "vertical" component of a horizontal velocity.
> I've also found that my students have difficulty distinguishing between
> (Delta v), v_avg, v_i, etc.  For example, I once asked students to
> consider an object that starts from rest and accelerates at a constant
> rate.  If the change in velocity is 122.5 m/s toward the north, what is
> the average velocity?
> A. 245 m/s [0%]
> B. 122.5 m/s [61%]
> C. 61.25 m/s [39%]
> D. zero [0%]
>
> Further thoughts?
>
> ____________________________________________________
> Robert Cohen, Chair, Department of Physics
> East Stroudsburg University; E. Stroudsburg, PA 18301
> 570-422-3428; www.esu.edu/~bbq

--
"Trust me.  I have a lot of experience at this."
                General Custer's unremembered message to his men,
                just before leading them into the Little Big Horn Valley