Schenker, Meaghan – Homework 4 – Due: May 10 2008, midnight – Inst: Peter LeMaire
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Physics 121 Homework 4
001
(part 1 of 1) 10 points
An Atwood machine is constructed using a
hoop with spokes of negligible mass.
The
2
.
3 kg mass of the pulley is concentrated on
its rim, which is a distance 24 cm from the
axle. The mass on the right is 1
.
36 kg and on
the left is 1
.
69 kg.
1
.
3 m
2
.
3 kg
24 cm
ω
1
.
69 kg
1
.
36 kg
What is the magnitude of the linear accel
eration of the hanging masses? The accelera
tion of gravity is 9
.
8 m
/
s
2
.
Answer in units of
m
/
s
2
.
002
(part 1 of 1) 10 points
A horizontal 641 N merrygoround of radius
1
.
14 m is started from rest by a constant
horizontal force of 43
.
7 N applied tangentially
to the merrygoround.
The acceleration of gravity is 9
.
8 m
/
s
2
.
Assume it is a solid cylinder.
Find the kinetic energy of the merrygo
round after 2
.
29 s. Answer in units of J.
003
(part 1 of 3) 10 points
A 14
.
8 kg object is attached to a cord that
is wrapped around a wheel of radius 11
.
6 cm,
as shown.
The acceleration of the object
down the frictionless incline is measured to be
0
.
76 m
/
s
2
.
Assume the axle of the wheel to
be frictionless.
The acceleration of gravity is 9
.
8 m
/
s
2
.
14
.
8 kg
0
.
76 m
/
s
2
37
◦
11
.
6 cm
Note:
Figure is not drawn to scale
Find the tension in the rope.
Answer in
units of N.
004
(part 2 of 3) 10 points
Find the moment of inertia of the wheel. An
swer in units of kg
·
m
2
.
005
(part 3 of 3) 10 points
Find the angular speed of the wheel 2
.
33 s
after it begins rotating, starting from rest.
Answer in units of rad
/
s.
006
(part 1 of 3) 10 points
The blocks shown in figure are connected by
an inextensible string of negligible mass. The
string passes over a frictionless pulley without
slipping on the rim of the pulley.
The acceleration of gravity is 9
.
8 m
/
s
2
.
The block on the frictionless incline is mov
ing with a constant acceleration up the in
cline.
24 kg
T
1
R
= 0
.
13 m
M
6
.
9 kg
μ
= 0
T
2
5
.
9 m
/
s
2
30
◦
Determine the tension
T
1
in the vertical
part of the string. Answer in units of N.
007
(part 2 of 3) 10 points
Determine the tension
T
2
in the string parallel
to the incline plane. Answer in units of N.
008
(part 3 of 3) 10 points
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Schenker, Meaghan – Homework 4 – Due: May 10 2008, midnight – Inst: Peter LeMaire
2
Assume:
The pulley has uniform density and
is shaped like a narrow cylindrical disk.
Find the mass
M
of the pulley. Answer in
units of kg.
009
(part 1 of 1) 10 points
Consider two masses, 3
.
2 kg and 6
.
9 kg, con
nected by a string passing over a pulley having
a moment of inertia 11 g m
2
about its axis of
rotation, as in the figure below.
The string
does not slip on the pulley, and the system is
released from rest. The radius of the pulley is
0
.
29 m.
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 Spring '08
 LeMaire
 Physics, Energy, Mass, Work, Peter LeMaire

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