This preview shows pages 1–3. Sign up to view the full content.
Lesson 4.5 Homework Solutions
1.
What is the value g on the surface of a planet that has twice the mass
of the earth and a radius 1.5 times the radius of the earth?
If g is the acceleration due to gravity on earth and g’ the acceleration
due to gravity on the other planet, we have
2
2
2
2
2
2
2
2
'
(1.5
)
2.25
2.25
2.2
0
5
.89
e
e
e
e
e
e
e
e
G
GM
g
R
G
M
GM
g
g
R
R
g
M
R
=
⋅
=
=
=
⋅
=
=
2.
Calculate the force of gravity on a spacecraft 8000 km from the
surface of the earth if its mass is 1600 kg.
If g is the acceleration due to gravity on earth and g’ the acceleration
due to gravity at the spacecraft, we have
( 29
2
2
2
6 2
2
2
6
6
2
'
(
)
'
(6.38 10 )
0.2
(
)
6.38 10
8 10
'
0.2
1.96
e
e
e
e
e
e
GM
g
R
GM
g
R
h
g
R
g
R
h
g
g
ms

=
=
+
×
=
=
=
+
×
+ ×
=
=
Force of gravity on the spacecraft = mg’ = 1600
×
1.96 =
3136 N
3.
What is the value of g at an altitude of 450 km above the surface of
the earth?
Let g’ be the acceleration due to gravity at an altitude h = 450 km
2
2
2
6 2
14
6
5 2
2
13
'
(
)
(
)
9.8 (6.38 10 )
3.99 10
'
(6.38 10
4.5 10
8.56 m
)
6
1
s
4. 6
0
e
e
e
e
GM
gR
g
R
h
R
h
g
=
=
+
+
×
×
×
=
=
=
×
+
×
×
This preview has intentionally blurred sections. Sign up to view the full version.
View Full Document 4
.
The average distance of Neptune from the sun is 4.5 x 10
9
km. Using
the fact that the earth is 1.5 x 10
8
km from the sun, compute the length
of Neptunian year.
T
n
– Period of Neptune, T
e
– Period of earth, r
n
– average distance of
Neptune from the sun, r
e
– average distance of earth from the sun.
2
This is the end of the preview. Sign up
to
access the rest of the document.
This note was uploaded on 05/01/2011 for the course PHY 2048 taught by Professor George during the Fall '10 term at Edison State College.
 Fall '10
 George
 Physics, Acceleration, Gravity, Mass, Work

Click to edit the document details