homework 14 – KIM, JI – Due: Apr 27 2008, 4:00 am
1
Question 1, chap 36, sect 3.
part 1 of 3
10 points
A spaceship travels with a speed of 0
.
8
c
as
it passes by the Earth on its way to a distant
star, as shown in the diagram below. The
pilot of the spaceship measures the length of
the moving ship as 30 m.
0
.
8 c
Earth
Determine its length as measured by a per
son on Earth.
Correct answer: 18 m (tolerance
±
1 %).
Explanation:
Let :
L
0
= 30 m
and
v
= 0
.
8
c.
Applying length contraction,
L
=
L
0
γ
=
L
0
r
1
−
v
2
c
2
= (30 m)
R
1
−
(0
.
8
c
)
2
c
2
=
18 m
.
Question 2, chap 36, sect 3.
part 2 of 3
10 points
The pilot of the spaceship observes that the
spaceship travels for 8 years.
Determine how much time has passed ac
cording to a person on Earth.
Correct answer: 13
.
3333 years (tolerance
±
1
%).
Explanation:
Δ
T
=
Δ
T
0
γ
= 8 years
×
1
.
66667 =
13
.
3333 years
.
Question 3, chap 36, sect 3.
part 3 of 3
10 points
Some time after passing the Earth, the pilot
shoots a laser pulse backward at a speed of
3
×
10
8
m
/
s with respect to the spaceship.
Determine the speed of the laser pulse as
measured by a person on Earth.
Correct answer: 3
×
10
8
m
/
s (tolerance
±
1
%).
Explanation:
A laser pulse travels at the speed of light, in
dependent of the frame in which it is measured
( the key point of special relativity). Thus the
Earth observer sees the pulse traveling at the
same speed as the pilot,
3
×
10
8
m
/
s
.
Question 4, chap 36, sect 3.
part 1 of 2
10 points
Two Frecrackers explode at the same place
in a rest frame with a time separation of 14 s
in that frame.
±ind the time between explosions, as mea
sured in a frame moving with a speed 0
.
6 c
with respect to the rest frame according to
classical physics without the special theory of
relativity.
Correct answer: 14 s (tolerance
±
1 %).
Explanation:
According to classical physics:
t
=
t
0
= 14 s
.
Question 5, chap 36, sect 3.
part 2 of 2
10 points
±ind the time between explosions, as mea
sured in a frame moving with a speed 0
.
6 c
with respect to the rest frame according to
the special theory of relativity.
Correct answer: 17
.
5 s (tolerance
±
1 %).
Explanation:
This preview has intentionally blurred sections. Sign up to view the full version.
View Full Documenthomework 14 – KIM, JI – Due: Apr 27 2008, 4:00 am
2
According to the special theory of relativ
ity:
t
=
t
0
r
1
−
(
v
c
)
2
=
(14 s )
r
1
−
(
0
.
6 c
c
)
2
= 17
.
5 s
.
Question 6, chap 36, sect 4.
part 1 of 1
10 points
Rods
P
and
Q
are at rest in an inertial
reference frame and oriented as shown. Both
rods have length
L
in this reference frame.
A person moves at a relativistic speed in the
positive
x
direction.
x
y
Q
L
P
L
O
Which of the following would be the
lengths, as compared to
L
, observed for these
rods by the person?
P
This is the end of the preview. Sign up
to
access the rest of the document.
 Spring '08
 Turner
 Physics, Work, Special Relativity, Correct Answer

Click to edit the document details