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FINAL EXAM Chapters 1  14
Spring 2005
1
Name:
Posting Code ____ ____ ____
(only if you want your grade posted on the web.)
Solve the following problems in the space provided. Use the back of the page if needed. Each
problem is worth 10 points. You must
show your work in a logical fashion starting
with the
correctly applied physical principles shown on the last page. Your score will be maximized if
your work is easy to follow because partial credit will be awarded.
1. A helicopter flying horizontally at 30.0m/s is 80.0m above the ground and plans to drop
supplies to tsunami victims below. Find (a)the time before they are directly overhead that they
must release the supplies so that they land near these victims and (b)the horizontal distance from
where they release them to the point where they land.
(a)Using the kinematic equation along the ydirection,
y
=
y
o
+
v
oy
t
+
1
2
a
y
t
2
Plugging in the numbers,
0
=
y
o
+
1
2
a
y
t
2
"
t
=
#
2
y
o
a
y
=
#
2(80.0)
#
9.80
"
t
=
4.04
m
/
s
.
(a)Using the kinematic equation along the xdirection,
x
=
x
o
+
v
ox
t
+
1
2
a
x
t
2
Plugging in the numbers,
x
=
v
ox
t
"
x
=
(30.0)(4.04)
"
x
=
121
m
.
2. A 150g meterstick is suspended horizontally from a string at
the 30cm mark that is wrapped over a pulley supporting a mass
M. Two weights hang from the stick. One has a mass of 100g at
the 80cm mark and the other is at the 5cm mark. Find the mass
at the 5cm mark and the mass M needed to keep the meterstick
in equilibrium.
Applying the Second Law for Rotation about the origin,
"
#
=
I
$
%
25
Mg
45
mg
75
m
2
g
=
0
Solving for M,
M
=
45
m
+
75
m
2
25
=
45(150)
+
75(100)
25
"
M
=
570
g
.
Applying the Second Law along the ydirection,
"
F
y
=
ma
y
#
Mg
$
mg
$
m
1
g
$
m
2
g
=
0
Solving for m
1
,
m
1
=
M
"
m
"
m
2
=
570
"
150
"
100
#
m
1
=
320
g
.
x
y
v
o
h
x
o
= 0
x = ?
v
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 Fall '09
 Kagan
 Physics

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