chauhan (mmc2762) – Ch4H2 – turner – (56910)
1
This printout should have 12 questions.
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beFore answering.
001
10.0 points
IF a chain oF 30 identical short springs linked
end to end has a sti±ness oF 240 N
/
m, what is
the sti±ness oF one short spring?
Correct answer: 7200 N
/
m.
Explanation:
Springs in series have the e±ective sti±ness
K
, where
K
is given in terms oF the sti±nesses
oF the individual springs as Follows:
1
/K
= 1
/k
1
+ 1
/k
2
+
· · ·
+ 1
/k
N
.
²or identical springs, we have
k
=
NK
, where
k
is the sti±ness oF a single spring. ThereFore
k
= (30)(240 N
/
m)
=
7200 N
/
m
.
002
10.0 points
You place 40 identical springs side by side (in
parallel) and connect them to a large, massive
block. The sti±ness oF the 40spring combi
nation is 20025 N
/
m. What is the sti±ness oF
one oF the individual springs?
Correct answer: 500
.
625 N
/
m.
Explanation:
Springs in parallel have an e±ective sti±ness
K
, where
K
is given in terms oF the sti±nesses
oF the individual springs as Follows:
K
=
k
1
+
k
2
+
· · ·
+
k
N
.
²or identical springs, we have
K
=
Nk
, or
k
=
K/N
, where
k
is the sti±ness oF a single
spring.
ThereFore,
k
=
20025 N
/
m
40
=
500
.
625 N
/
m
.
003 (part 1 of 4) 10.0 points
One mole oF tungsten (6
.
02
×
10
23
atoms)
has a mass oF 184 g, and its density is
19
.
3 g
/
cm
3
, so the centertocenter distance
between atoms is 2
.
51
×
10

10
m. You have
a long, thin bar oF tungsten, 2
.
8 m long, with
a square cross section, 0
.
1 cm on a side. You
hang the rod vertically and attach a 420 kg
mass to the bottom, and you observe that
the bar becomes 1
.
24 cm longer. ²rom these
measurements, it is possible to determine the
sti±ness oF one interatomic bond in tungsten.
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 Spring '11
 Antoniewicz
 Physics, Atom, Mole, Correct Answer, rod, Chauhan

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