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Double the RMS Speed
001
1
points
A gas is at 35
◦
C
To what temperature must it be heated to
double the rms speed of its molecule
Correct answer: 959
◦
C
Explanation:
Let :
T
i
35
◦
C
3
K
.
v
f,rms
2
v
i,rms
At a given temperature, the kinetic energy is
K
1
2
v
2
rms
3
2
k
B
T
Thus
T
f
T
i
1
2
v
2
f,rms
1
2
v
2
i,rms
(2
v
i,rms
)
2
v
i,rms
4
.
T
f
4
T
i
4 (3
K)
1232 K
959
◦
C
Hydrogen Thermal Energy
002
1
points
A box contains about 6
.
6
×
1
21
hydrogen
atoms at room temperature 21
◦
C
ind the thermal energy of these atoms
Correct answer: 41
.
74 6 J
Explanation:
Given :
N
6
.
6
×
1
21
and
T
21
◦
C
K .
Thermal energy for one atom is
E
3
2
k T,
so the thermal energy for N atoms is
E
3
2
N k T
3
2
(
6
.
6
×
1
21
) (
1
.
3
×
1
−
23
J
/
K
)
×
(294 K)
41
.
74 6 J
.
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 Fall '09
 RichardScalettar
 Energy, Kinetic Energy, Potential Energy, Correct Answer

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