### Quiz 2014.10.08

```A uniform wire is bent as shown. Which of the
points shown in the diagram best shows the
location of the center of mass of the wire? The
dotted line shown connects the midpoints of the
straight pieces of the wire.
Po
in
tE
0%
Po
in
0%
tD
0%
tC
tB
0%
Po
in
tA
0%
Po
in
Point A
Point B
Point C
Point D
Point E
Po
in
A.
B.
C.
D.
E.
Two discs of radii 8.0 cm
and 4.0 cm are made of
cardboard and are placed
on a flat table as shown.
How far from the center of
the larger disc is the
center of mass of the
entire figure located?
cm
0%
9.
6
6.
0
4.
0
0%
cm
0%
cm
0%
cm
cm
0%
2.
4
cm
0%
3.
0
2.0 cm
2.4 cm
3.0 cm
4.0 cm
6.0 cm
9.6 cm
2.
0
A.
B.
C.
D.
E.
F.
Three tiny balls of equal mass are
placed on a horizontal frictionless
surface at the corners of an equilateral
triangle (all of the sides are 2 m and all
of the angles are 60°). What are the x
and y coordinates of the center of mass
of the system formed by the three
balls? (The y-axis passed through the
top ball and the x-axis passed through
the bottom balls.)
0%
0%
0%
=0
x=
.8
0.
7
67
m
m
;y
=0
.6
x=
7
0
m
m
;y
=0
.6
7
m
m
x=
0
;y
m
x=
0
;y
=0
.5
8
m
=1
m
;y
=0
x=
0
;y
0%
m
0%
m
0%
m
x=0 m; y=0 m
x=0 m; y=1 m
x=0 m; y=0.58 m
x=0 m; y=0.87 m
x=0.67 m; y=0.67 m
x=0 m; y=0.67 m
x=
0
A.
B.
C.
D.
E.
F.
Four particles are located in a coordinate plane. Their masses and x- and
y-coordinates are given in the table (except for the coordinates of
particle m4 ). Find those coordinates if the center of mass of all four
particles is located at the origin?
cm
=
;y
4
cm
1.
5
=
x4
0%
2.
5
cm
=
4
;y
cm
-2
=
x4
-1
.5
=
x4
0%
7
2.
5
=
4
;y
cm
2
=
x4
0%
cm
cm
=
4
;y
=
;y
4
cm
1.
5
=
x4
0%
7
-2
.5
cm
-7
=
4
;y
cm
-2
=
0%
cm
0%
cm
x4 = -2 cm; y4 = -7 cm
x4 = 1.5 cm; y4 = -2.5 cm
x4 = 2 cm; y4 = 7 cm
x4 = -1.5 cm; y4 = 2.5 cm
x4 = -2 cm; y4 = 7 cm
x4 = 1.5 cm; y4 = 2.5 cm
x4
A.
B.
C.
D.
E.
F.
A large person with mass 2M and a smaller person with mass M
are holding onto a massless pole while standing on frictionless
ice, as shown below. If the large person pulls himself toward the
smaller person along the massless rod, where will they meet?
0%
e
o
f
th
e
ab
o
ve
3m
0%
2m
0%
on
0%
N
0%
1m
0%
0
0%
-1
m
0%
-2
m
-3m
-2m
-1m
0
1m
2m
3m
None of the above
-3
m
A.
B.
C.
D.
E.
F.
G.
H.
```