scott_3 - 211S10
 
 (a) (b) (c) (d) 
 (e) 
 (f) 
...

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Unformatted text preview: 211S10
 
 (a) (b) (c) (d) 
 (e) 
 (f) 
 
 General
comments
on
homework
 I
hereby
declare
the
first
homework
to
be
practice.

Everyone
gets
100%.

This
is
not
because
you
all
bombed
 it.

You
did
better
than
the
people
in
the
Spring
09
class
and
possibly
a
little
worse
than
those
in
the
Fall
09
 class,
but
about
as
expected.
 
 Since
the
format
is
so
different,
people
generally
makes
lots
of
mistakes
from
simple
confusion,
I
see
no
 reason
to
effectively
punish
people
for
not
getting
it
right
when
they’ve
never
seen
the
right
way
to
do
it
 before
and
haven’t
ever
gotten
feedback
on
their
interpretation
of
the
right
way.
 
 This
will
be
the
only
practice,
however.

Next
time
counts.

See
the
attached
copy
of
a
homework
solution
 from
last
semester
for
an
additional
example.
 
 I
will
go
over
everyone’s
homework
with
you
individually
during
our
30‐minute
meeting
this
week.

 Therefore,
the
second
homework
will
be
due
next
Monday
the
8th
at
the
same
time
the
3rd
homework
is
 due
so
you
have
time
to
make
use
of
the
discussion.
 
 You
don’t
need
to
repeat
the
question
unless
you
want
to.

I
am
not
a
fan
of
unnecessary
work.

I
am
a
rabid
 fan
of
necessary
work
however,
hence
the
demand
that
you
give
arguments
for
your
conclusions.

Without
 those,
the
homework
devolves
into
empty
calculation.
 
 You
don’t
need
to
type
your
answers.

Hand
written
will
do.

Only
graphs
need
to
be
made
by
computer.

I
 allowed
handwritten
graphs
last
semester
and
the
results
were
not
good.
 There
is
seldom
the
right
answer.

Often
there
are
many
different
valid
paths
to
the
correct
conclusion.

I
 don’t
care
which
one
you
give
(actually
I
prefer
unique
ones,
teaching
the
same
thing
over
and
over
gets
 boring
and
I
have
to
read
~30
solutions
to
each
problem
each
semester)
as
long
as
it’s
good.
 Imagine
that
you
had
to
explain
why
the
answer
is
what
it
is
to
someone
else
and
the
only
interaction
you
 will
have
with
them
will
be
through
your
written
homework
solution.

Imagine
that
your
grade
depended
on
 whether
or
not,
after
they
had
read
your
solution,
they
could
explain
it
correctly
to
me.
 
 Write
your
solution
so
that
you
would
get
an
A
in
that
case.

Remember
that
what
is
obvious
to
you
is
 distinctly
non‐obvious
to
many
other
people.
 
 Things
I
will
take
points
off
for:
 
 (1) Numbers
where
they
aren’t
supposed
to
be
and
no
numbers
where
they
are
supposed
to
be.
 
 Last
semester
I
never
asked
a
question
on
the
homework
that
required
a
numerical
answer
until
near
the
 end
of
the
semester.

The
result
was
that
when
I
did
I
got
utterly
impossible
answers.

So
this
semester
there
 are
two
types
of
problems,
the
first
is
symbolic,
for
example
problem
#1.

The
second
is
numeric,
for
 example
problem
#2.

The
numeric
problems
are
given
a
title
indicating
that,
most
often
they’re
called
just
 ‘Numbers’.
 
 The
numeric
problems
exist
for
the
purpose
of
calculating
the
size
of
things
so
that
you
can
learn
to
 recognize
when
answers
are
too
big
or
too
small;
I
don’t
care
about
significant
figures,
nor
do
I
care
about
 exactness
in
general,
hence
my
refusal
to
define
how
high
a
storey
is,
you
can
estimate
a
reasonable
number.

 For
example,
when
we
get
to
gravity,
I
will
ask
you
for
the
force
on
you
from
the
Earth;
you
should
know
 that
if
you
get
1,486,231,385,238
Newtons,
that
must
be
wrong.
 
 (2) There
will
be
few
further
questions
with
plots
but
you
need
to
know
what
a
good
plot
contains
because
not
 having
the
right
things
in
it
renders
it
mostly
useless.
 
 See
the
attached
plot
for
what
a
correct
plot
contains.

Briefly,
the
plot
must
say
what
it
is
a
plot
of,
it
must
 say
what
the
axes
are
and
what
units
they’re
in,
and
you
should
distinguish
between
theoretical
plots
and
 experimental
ones.

Experimental
data
is
always
discrete,
theoretical
is
usually
continuous,
so
no
solid
lines
 unless
they’re
calculated.

We’re
never
going
to
have
experimental
data
in
this
class;
so
all
your
plots
will
 probably
be
solid
lines.
 
 (3) (4) 
 Just
Math
 
 From
here
on
out
you
will
definitely
lose
points
if
you
just
give
me
a
series
of
equations.

You
must
explain
 what
you
are
doing
physically
and
only
then
give
me
the
mathematical
equivalent.
 
 Just
Math
In
Words
 Your
explanations
must
be
more
that
just
restatements
of
the
mathematical
step
you
are
about
to
take.

 They
must
be
reasons
for
that
step.

For
example,
here
is
a
paragraph
from
the
middle
of
my
solution
to
a
 homework
problem
from
last
semester:
 
 
 (5) 
 Because of the table, the normal force must cancel the gravitational force on A, and everything else is moving in a straight line, so we can get rid of the vectors, taking care to have the right signs (Block A will go left, so blocks B and C will go down, thus I expect a to be in the same direction as TAB, m, and TBC for B, while it must be in the opposite direction of TBC for C), … Too
Much
Math
 Do
not
show
me
every
algebraic
step.

If
you
have
an
equation
relating
‘y’
and
‘a’
and
you’re
solving
it
for
‘a’,
 just
give
me
the
starting
and
ending
equations.

You
already
got
a
grade
for
your
ability
to
do
algebra,
that
 bit
doesn’t
count
for
anything
any
more.
 
 (6) 
 Being
wrong
 For
the
sake
of
explicitness
of
the
rules,
you
have
to
be
right
to
get
full
credit.
 
 
 Ignore
the
above
at
your
peril.

Every
semester
two
or
three
people
consider
rules
1‐6
somehow
optional,
as
if
I
 didn’t
really
mean
it.

That’s
a
great
way
to
get
50%
off.


 
 But
don’t
sweat
it
either,
after
the
third
homework,
most
people
get
90‐100%:
 
 
 Final HW Scores 100 A B C D HW score 80 60 40 20 0 0 5 10 Student 15 20 25 
 ...
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This note was uploaded on 12/13/2011 for the course PHYS 521 taught by Professor Staff during the Fall '10 term at South Carolina.

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