Ch3-HW1
–
florin
–
(56950)
1
This print-out should have 23 questions.
Multiple-choice questions may continue
on the next column or page
–
find all
choices before answering.
Problem @22: calculate the di
ff
erence in
the magnitudes of the fields, not the forces.
001 (part 1 of 4) 10.0 points
Each part of this problem will state an ex-
ample of objects interacting via some
force. Choose the fundamental interaction
that is responsible in each case.
A neutron outside a nucleus decays
into a proton, electron, and antineutrino.
1. Strong
2. Gravitational
3. Weak correct
4. Electromagnetic
Explanation:
Notice the presence of an antineutrino in
this decay. Neutrinos (and their antiparticle
partners) only interact via the weak force, so
this must be a weak interaction.
002 (part 2 of 4) 10.0 points
Protons and neutrons attract each other in
a nucleus.
1. Gravitational
2. Strong correct
3. Weak
4. Electromagnetic
Explanation:
The force that holds the nucleus together
must be strong enough to overcome the repul-
sion between protons due to the electromag-
netic force. This is a strong interaction.
003 (part 3 of 4) 10.0 points
The Earth pulls on the Moon.
1. Gravitational correct
2. Weak
3. Electromagnetic
4. Strong
Explanation:
This is a gravitational interaction, in
which massive bodies attract each other.
004 (part 4 of 4) 10.0 points
Protons in a nucleus repel each other.
1. Gravitational
2. Weak
3. Electromagnetic correct
4. Strong
Explanation:
This
is
an
example
of
an
electromagnetic in-teraction, in which
particles with like charges repel.
005 (part 1 of 2) 10.0 points
The
mass
of
the
Sun
is
2 × 10
30
kg,
and
the
mass
of
Mercury
is
3.3 × 10
23
kg.
The
distance
from
the
Sun
to
Mercury
is
4.8 × 10
10
m.
First, calculate the magnitude of the gravi-
tational force exerted by the Sun on Mercury.
Use G = 6.67 × 10
−
11
m
3
.
kg · s
2
Correct answer:
1.91068 × 10
22
N.
Explanation:
The magnitude of the gravitational
force between two objects is given by
F
~
gr
=
₃
−
Gm
1
m
2
₃
=
Gm
1
m
2
.
₃
₃
2
2
₃
₃
₃
₃
r
r
₃
₃
₃
₃
₃
₃
We just need to plug in the given
constants to find the answer:
₃
F
~
gr
₃
=
Gm
1
2
m
2
₃
₃
r

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