Physics 140 Winter 2004 Midterm 3
1
1.
(P) The figure below shows an 18.0kg crate of salami sliding down a ramp on a
(massless) rope that is wrapped around a disk of radius 0.25m and mass 6.0kg.
The
coefficient of kinetic friction between the crate and ramp is
μ
k
=0.24.
What is the
magnitude of the disk’s angular acceleration?
a)
3.1 rad/s
2
b)
6.7 rad/s
2
c)
9.8 rad/s
2
d)
11.4 rad/s
2
e)
13.7 rad/s
2
2.
(P) A uniform solid sphere rests suspended from a cord anchored at point P along an
inclined plane.
Which of the following statement(s) is(are)
true
?
C
P
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2
3.
(P) A rigid assembly consists of a thin hoop of radius
R
and mass
m
attached to a thin
rod also of mass
m
and length 2
R
rests in the vertical position shown in the figure
below.
Given a tiny nudge (involving negligible energy) from behind, the assembly
rotates about the horizontal axis shown.
What is its angular speed as it passes through
the inverted (upside-down) orientation?
a)
(96g/65
R
)
1/2
b)
(33g/15
R
)
1/2
c)
(48g/17
R
)
1/2
d)
(17g/12
R
)
1/2
e)
(8mg/15
R
)
1/2
4.
Kepler’s second law of planetary motion – the observation that the orbits of planets
sweep out equal areas around the Sun in equal times – mainly reflects the
conservation of which physical quantity?
rotation
axis
hoop
rod
3
5.
Three coplanar bodies A, B and C with masses
m
, 2
m
, and 8
m
, respectively, are
shown below.
At what (
x,y
) location should a fourth body D of mass 8
m
be placed
such that the total gravitational force on body A is zero?
a)
( –2
1/4
d
, 2
1/4
d
)
b)
(2
1/4
d
,
d
/2
1/4
)
c)
(2
1/4
d
, –2
1/4
d
)
d)
(
d
/2
1/4
, –
d
/2
1/4
)
e)
(
d
/2
1/4
, –2
1/4
d
)
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- Winter '07
- Evrard
- Angular Momentum, Force, Friction, Kinetic Energy, Mass, rod B
-
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