Module 5
.
1
Post the problems you will have in your problem
set ASAP so no other student will
.
select the problem
.
2
,
.
If you have trouble with the problem post your question on the discussion Cafe
You will not be able to see other postings on your problems until you have posted your
.
solutions
,
You must state which problem you are doing you may have to include a


free body diagram
or other diagram if it helps your
.
discussion
You must show units
and
.
explain each step
The
format that is
used in the text book
is similar to
the
way
.
you will discuss the problem
.
3
,
If you have problems with the problem you will have
the opportunity to ask the
.
group for help
Other class members will have the
opportunity to help with the
.
problem and earn some points
.
4
.
You must critique your classmate's work
(
"
"
.)
Saying good job is not appropriate
.
You cannot fall behind in class
Module
5 covers chapters
11
and
.
12
:
Chapter
:
11
.
5
The karat is a dimensionless unit that is used to indicate the proportion of gold

.
in a gold containing alloy
An alloy that is one karat gold contains a weight of pure
.
gold that is one part in 24
. 
.
What is the volume of gold in a 14 0 karat gold necklace whose weight is 1 27 N?
:
Mass of gold alloy
=
=
=
W mg Wg m
.
.
/
≈ .
1 27 N9 80 m s2 0 1296 kg
:
Volume of gold alloy
=
=
=
ρ mV mρ V
.
.
/
≈ .

= .
0 1296 kg19 3 x 103 kg m3 6 7146 x 10 6 m3 6 7146 cm3
:
Volume of pure gold in alloy
.
≈ .
= .
14246 7146 cm3 3 91685 cm3 3 92 cm3
.
13
(
.
Interactive solution 11 13 at
.
.
/
/
www wiley com college cutnell
is a model for this
).
.
problem
A solid concrete block weighs 169 N and is resting on the ground
Its
.
.
.
.
dimensions are 0 400 m x 0 200 m x 0 100 m
A number of identical blocks are
.
stacked on top of this one
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What is the smallest number of whole blocks including the one on the ground that can
be stacked so that their weight creates a pressure of at least two atmospheres on the
ground beneath the first block?
=
P FA
= .
* .
= .
A 0 200m 0 100 m 0 02 m2
= .
1 atm 1 013 x 105Pa
= +
.
2 atm n 1169 N0 02 m2
+ = * .
.
= .
.
= .
n 1 2 1 013 x 105Pa0 02 m2169 N 2 026 x 105 Pa0 02 m2169 N 4 052 x 103
/
≈
.
Pa m2169 N 23 976
+ =
.
n 1 23 976
=
n 23
23 whole blocks will create 2 atmospheres of pressure on the ground beneith the first
block
:
INSTRUCTORS NOTES
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 Spring '10
 BRUMM
 Physics, Thermodynamics, Mass flow rate, air gap

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