This preview shows pages 1–2. Sign up to view the full content.
noon on Friday, Dec. 4.
1. Serway 13.1
Answer:
Because of constant nuclear density we have
r
=
r
0
A
1
/
3
with
r
0
= 1
.
2
×
10

15
m
so
4
2
H has
r
= (1
.
2
×
10

15
)(4)
1
/
3
= 1
.
9
×
10

15
m
238
92
U has
r
= (1
.
2
×
10

15
)(238)
1
/
3
= 7
.
4
×
10

15
m
so the ratio is
(238
/
4)
1
/
3
= 3
.
9
which is modest for such a large mass ratio of
238
/
4
≃
60
.
2. Serway 13.5
Answer:
The turnaround point is when all of the alpha particle’s kinetic energy goes into
electrostatic potential energy, or
E
k
=
1
4
πǫ
0
Z
α
Z
r
so
r
=
Z
α
Z
4
πǫ
0
E
k
=
(2)(79)
4
π
(8
.
85
×
10

12
)
·
(0
.
5
×
10
6
eV
)
·
(1
.
602
×
10

19
J/eV
)
= 4
.
5
×
10

13
m
or 450 fm. To approach within 300 fm we must have a kinetic energy of
E
k
=
1
4
πǫ
0
(2)(79)(1
.
602
×
10

19
Coulomb
)
2
300
×
10

15
= 1
.
21
×
10

13
Joules
or if we divide by
1
.
602
×
10

19
J/eV an energy of 0.75 MeV. This energy is small compared
to the alpha particle rest mass of about
4
·
940
MeV so we can find the velocity using a
nonrelativistic formula:
v
=
r
2
E
k
m
=
r
2
E
k
mc
2
·
c
=
r
2
·
0
.
75
4
·
940
·
2
.
99
×
10
8
= 6
.
0
×
10
6
m/s
.
3. Serway 13.9
Answer:
We assume that the net atomic weight of copper
m
is due to a fraction
x
times the
weight
m
63
of
63
Cu and a fraction (
1
−
x
) of the weight
m
65
of
65
Cu. That is,
m
=
xm
63
+ (1
−
x
)
m
65
m
−
m
65
=
x
(
m
63
−
m
65
)
x
=
m
−
m
65
m
63
−
m
65
=
63
.
55
−
64
.
95
62
.
95
−
64
.
95
= 0
.
70
so we have 70%
63
Cu and 30%
65
Cu.
4. Serway 13.16. Additional places to get atomic masses are at
http://physics.nist.gov/PhysRefData/Compositions/index.html
and
http://www.nndc.bnl.gov/nudat2/
Answer:
The desired reaction is
This preview has intentionally blurred sections. Sign up to view the full version.
View Full Document
This is the end of the preview. Sign up
to
access the rest of the document.
This note was uploaded on 05/28/2011 for the course PHY 251 taught by Professor Rijssenbeek during the Fall '01 term at SUNY Stony Brook.
 Fall '01
 Rijssenbeek
 Physics, Work

Click to edit the document details