Quiz+1+solution - Quiz
1
Physics
2
Section
C


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Unformatted text preview: Quiz
1
Physics
2
Section
C
 October
1,
2010
 1) M
can
run
3
miles
in
the
time
it
takes
J
to
run
2
miles
and
K
to
run
1
 mile.
M,
J
and
K
take
part
in
a
long
distance
relay
where
each
person
 runs
1
mile.
They
finish
the
race
in
33
minutes.

How
long
does
J
take
 to
run
ONE
mile?
 
 Let
time
for
M
to
run
3
miles
be
T
 Then
M
takes
T/3,
J
takes
T/2
and
K
takes
T
to
run
a
mile
 T/3+T/2+T
=
33
minutes
 T=18
minutes
 J
takes
9
minutes
to
run
one
mile
 
 
 2) M
has
a
partially
filled
container
of
water
with
some
special
chemical
 called
TLAS
dissolved
in
it.
She
is
about
to
measure
the
concentration
 of
this
chemical
when
J
pours
distilled
water
that
has
no
TLAS
into
 the
container.
(J
and
M
hate
each
other
if
you
must
know.)
Luckily
M
 sees
that
J
has
poured
a
full
ONE‐liter
bottle
of
distilled
water
into
 the
beaker.
M
measures
the
volume
of
liquid
in
the
beaker
to
be
2.5L
 after
J
does
her
deed.
She
measures
the
concentration
of
TLAS
in
this
 2.5L
to
be
1.5%.
What
was
the
concentration
of
TLAS
in
the
original
 sample?


 
 Let
concentration
of
TLAS
in
the
original
sample
be
C1
 Then
C1*1.5L=2.5L*1.5%
 C1=2.5%.
 Quiz
1
Physics
2
Section
C
 October
1,
2010
 3) M
and
J
and
K
decide
to
mow
lawns
for
a
month
to
make
money.
M’s
 boyfriend
is
jealous
of
K
and
tells
M
that
K
is
not
working
hard
 enough.
J
hears
about
this
and
tells
M
that
his
girlfriend
is
just
plain
 crazy.
Here
is
the
data
J
has.
M
and
J
together
can
mow
a
1000
square
 feet
lawn
in
20
minutes.

M
and
J
and
K
all
working
together
can
mow
 a
2000
square
feet
lawn
in
25
minutes.
How
many
square
feet
of
 lawn
can
K
mow
by
himself
in
20
minutes?
Was
J
right
or
is
M’s
 girlfriend
right?

 
 Let
rates
for
mowing
lawn
for
M,
J
and
K
be
RM,
RJ
and
RK
 respectively
 RM+RJ
=
1000
sqft/
20
min
 RM+RJ+RK=2000
sqft/25
min
 Then
RK=(2000/25–1000/20)
sqft/min

 =
(80–50)
sqft/min=30
sqft/min
 So
in
20
minutes
K
can
mow
30
sqft/min*20min=600
sqft
by
 himself.
 This
is
more
than
half
of
what
M
and
J
together
mow.
So
K
is
 definitely
not
a
slacker
and
M’s
girlfriend
is
wrong.
 
 
 4) J
dislikes
seeing
milk
labeled
with
the
2.0%
and
1.0%
fat
content.
He
 goes
to
the
graduate
student
refrigerator
in
his
chemistry
lab,
pours
 out
all
the
2.0%
and
1.0%
milk
into
a
big
container
to
mix
everything
 and
then
pours
it
back
into
the
milk
bottles.
And
just
because
he
can,
 he
measures
the
fat
content
of
the
mixed
milk
to
be
1.6%.
Then,
in
 another
fit
of
madness,
he
decides
he
must
know
what
is
the
total
 volume
of
his
mixed
milk
in
the
refrigerator.
But
by
now
the
other
 grad
students
have
wised
up
and
put
a
lock
on
the
refrigerator.
So
J
 comes
to
you
for
help
and
tells
you
that
he
remembers
mixing
in
just
 ONE‐gallon
of
1%
milk.
What
is
the
total
volume
of
the
mixed
(1.6%)
 milk
in
the
refrigerator?
 
 Let
total
volume
of
mixed
milk
be
V
 Write
an
equation
for
the
fat
in
the
milk
 Then
(V–1gal)*2.0%+1gal*1%=V*1.6%
 V*2.0%
–
1gal*1%
=
V*1.6%
 V*0.4%=1gal*1%
 V=2.5gal
 Quiz
1
Physics
2
Section
C
 October
1,
2010
 Practice
problems
done
before
quiz.
 
 You
have
two
different
kinds
of
fruit
punch
named
Fruitopia
and
 Vegetopia.
Fruitopia
has
a
concentration
of
pure
fruit
juice
of
50%,
and
 the
pure
fruit
juice
concentration
of
Vegetopia
is
not
known.
You
mix
3
 parts
Vegetopia
and
2
parts
Fruitopia
to
come
up
with
your
very
own
 fruit
punch
named
Myopia.
You
do
some
tests
to
figure
out
that
Myopia
 has
a
pure
fruit
juice
concentration
of
40%.
Find
the
pure
fruit
juice
 concentration
of
Vegetopia
and
write
it
as
a
percentage
correct
to
two
 significant
figures.
 
 Let
the
fruit
juice
concentration
of
Vegetopia
be
C1.
 Then
3*C1+2*50%=5*40%
 C1=33%
 
 
 
 
A
couple
is
having
a
serious
fight
on
the
issue
of
who
earns
more
but
 neither
of
them
remembers
their
exact
salaries.
The
wife
got
a
raise
in
 salary
of
20%
that
has
been
in
effect
for
exactly
6
months
now.
The
 husband
does
remember
well
that
he
used
to
earn
$5,000
per
year
more
 than
the
wife
before
she
got
her
raise.
They
both
remember
(happily)
 that
their
total
income
(from
the
salaries)
for
the
last
12
months
was
 exactly
$100,000.
What
was
the
annual
salary
of
the
wife
before
she
got
 her
raise
correct
to
two
significant
figures
and
who
earns
more
now?
 
 Let
annual
salary
of
wife
before
raise
=
X
 Salary
of
wife
in
the
last
12
months
=
 X*6/12+(X+20%*X)*6/12=(2*X+0.2*X)/2=1.1*X
 Husband’s
salary
for
the
year=X+5000
 Then
(X+5000)+1.1*X=100000
 2.1*X=95000
 Annual
salary
of
wife
before
raise
$X=$4.5×104
(to
2
sig
figs)
 Annual
salary
of
wife
after
raise
1.2*$X=$5.4×104
(to
2
sig
figs)
 Annual
salary
of
husband
=$5.0×104
(to
2
sig
figs).

 So
wife
earns
more
now.
 ...
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This note was uploaded on 11/21/2010 for the course PHYSICS Physics 2 taught by Professor Manojkaplinghat during the Fall '10 term at UC Irvine.

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