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I attempted Peter's first problem. I did my best to be a lazy solver. I
wanted the general form of the equation of the parabola, using three points
on the trajectory. I chose to use [0,0], [20,35], and [80,0] Notice this
is a worst case for a very low pitch roof. I found the general form was
-7*x^2 +560*x -230*y = 0 using an online parabola calculator,
https://www.emathhelp.net/calculators/algebra-2/parabola-calculator/?type=d&p1x=0&p1y=0&p2x=20&p2y=35&p3x=80&p3y=0&dir=x
This provides about 5 meters headroom at the peak of the roof; a flight
time of 6.169 seconds (using Wolfram alpha at
https://www.wolframalpha.com/input?i=0+%3D+30.259*t+-+0.5*9.81*t%5E2
to solve the quadratic) at a launch velocity and angle of 32.93 m/s at
66.7 degrees.I expended two sheets of paper for working.
I have to suppose there is an easier way which eluded me.
On Friday, October 14, 2022 at 06:07:30 AM CDT, Anthony Lapinski via
Phys-l <phys-l@mail.phys-l.org> wrote:
Expecting too much? I don't know. Interesting problems? Well, we all think
our (physics) problems are interesting! Useful problems? Maybe. I'm not
sure what the (science) backgrounds of your students are. I teach at a
private high school. Over the years I've had to make the problems "easier"
(e.g., adding more parts to a problem). They still find them challenging.
The strong kids remain strong, but the weak kids are weaker. Plus there is
much grade inflation, test corrections, cheating (?), etc. And social media
and smartphones have made kids more distracted, less curious about science,
less patient, lazier, less caring about academics, harder to teach.
Nobody's fault. It's the world they have/know, and it's only getting worse.
Obviously a much bigger (and more important) discussion than the problems
you posed.
On Fri, Oct 14, 2022 at 6:32 AM Peter Schoch <pschoch@fandm.edu> wrote:
I teach at a community college. Due to rising tuition rates, our physicsmeters
classes have grown, mostly with those students who want to go on to
engineering majors when they transfer. Because of the increase, I can't
teach every section anymore and I hired an Adjunct who is a retired high
school AP physics teacher.
After much discussion, he's convinced that I am asking too much of the
students! His contention is that the problems I make them do for quizzes
and tests are too difficult for this level. For example, I just had them
do the following 2 problems:
1. You are standing 20 meters from a building. The building is 10
wide and 35 meters high. The second person is 50 meters from the otherthis
side of the building. With what initial speed and launch angle should a
ball be thrown to get to the second person.
HINT: The “peak” of the building (35 m) is located directly at the
midpoint of the building. To ensure that the ball clears the top of the
building, its height above the ground should be no less than 35.1m at
point.He
2. A uniform rope of length L has a mass M. It is stretched out along a
table with a portion of the rope, x, hanging over the edge of the table.
There
is a coefficient of friction, μ, between the rope and the table.
a. What fractional length of rope must be hanging off the table for it to
begin to move?
b. If there is sufficient rope hanging off the table, what is the
functional form of its velocity as a function of x?
I thought they were interesting problems that would be useful to them.
is adamant that the problems are too complex for Freshman.
Which brings me to my question -- am I expecting too much from these
students when asking such questions?
Thanks,
Peter Schoch
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