Name _______________________________________________________________________
Exam #1
Physics I
Spring 2007
If you would like to get credit for having taken this exam, we need
your name (printed clearly) at the top and section number below.
Your name should be at the top of every page.
Section #
_____ 1
_____ 2
_____ 4
_____ 5
_____ 7
_____ 9
_____ 10
_____ 11
_____ 12
_____ 14
_____ 15
M/R 8-10 (Bedrosian)
M/R 10-12 (Wilke)
M/R 12-2 (Yamaguchi)
M/R 2-4 (Yamaguchi)
M/R 4-6 (Wilke)
T/F 10-12 (Wetzel)
T/F 10-12 (Washington)
T/F 12-2 (Eah)
T/F 2-4 (Eah)
M/R 12-2 (Zhang)
M/R 2-4 (Bedrosian)
Questions
Part A
Value
24
Part B
20
C-1
24
C-2
32
Total
100
Score
You may not unstaple this exam.
Only work written on the same page as the question will be graded.
Cheating on this exam will result in an F in the course.
1
Name _______________________________________________________________________
On this exam, please neglect any relativistic and/or quantum mechanical effects. If you don’t
know what those are, don’t worry, we are neglecting them! On all multiple-choice questions,
choose the best answer in the context of what we have learned in Physics I.
On graphing and numerical questions, show all work to receive credit.
Part A – Multiple Choice – 24 Points Total (6 at 4 Points Each)
Write your choice on the line to the left of the question number.
______ 1.
The diagram below best represents which principle of physics?
A
A)
B)
C)
D)
______ 2.
A)
B)
C)
D)
E)
______ 3.
A)
B)
C)
D)
E)
F on A from B
F on B from A
B
Newton's First Law.
Newton's Second Law.
Newton's Third Law.
The Impulse-Momentum Theorem.
The system shown to the
4N
right consists of a cart on a
track, a string, a pulley,
and a hanging mass.
The weight of the cart is 4 N. The weight of the hanging mass is 4 N.
Friction of the cart on the track is a constant force of 2 N magnitude.
The mass of the string, the mass of the pulley, and the friction of the pulley
can be neglected.
What is the magnitude of the acceleration of the cart if g is the free-fall
acceleration?
g / 8.
g / 4.
g / 3.
g / 2.
g.
In the system in Question 2 above, what is the tension in the string?
1 N.
2 N.
3 N.
4 N.
8 N.
2
4N
Name _______________________________________________________________________
Questions 4-6 refer to an object moving in one dimension from t = 0 to t = 8 s.
The object begins at t = 0 s with velocity = 0 m/s and displacement = 0 m.
The graph of its acceleration is shown below.
a (m/s^2)
2
1
0
t (sec)
-1
2
4
6
8
-2
______ 4.
A)
B)
C)
D)
______ 5.
A)
B)
C)
D)
______ 6.
A)
B)
C)
D)
During which time intervals, if any, is the object slowing down? Select all correct
choices or put "0" if you think that none of the choices are correct.
0<t<2s
2<t<4s
4<t<6s
6<t<8s
At what time does the object reach its maximum displacement?
t=2s
t=4s
t=6s
t=8s
J is the net impulse on the object from 0 to 8 s. Which statement about J is correct?
J = 0.
J < 0.
J > 0.
There is insufficient information to determine the validity of A-C above.
3
Name _______________________________________________________________________
B – Graphing – 20 Points
An object of unknown mass moves in one dimension with momentum as shown in the graph
below from t = 0 to t = 10 seconds. Note that the curved portions of the graph are parabolas.
Graph the net force acting on the object as a function of time from t = 0 to t = 10 seconds.
Make sure your plots clearly show:
A. Any minimum or maximum points.
B. Whether the graph is curved or straight.
C. The values of net force at t = 0, 2, 4, 5, 6, 8, and 10 seconds.
Show all work, including what equations and/or principles of physics you are using.
Note: You may not assume an arbitrary value for the object’s mass to do this problem.
p (kg m/s)
2
1
0
-1
t (sec)
2
4
6
8
10
-2
Fnet (N)
0
t (sec)
2
4
6
8
10
4
Name _______________________________________________________________________
Problem C-1 (24 Points) – Cannon on a Mountainside
A cannon on a mountainside fired a cannonball at the valley below. The cannonball was 1470 m
above the valley when it was fired. It reached its maximum height 10.0 s after being fired.
Some time later, it hit the ground 2940 m in the horizontal (X) direction from where it was fired.
Neglect air resistance and use g = 9.8 m/s2.
What was the initial velocity of the cannonball (X and Y components)?
Show all work, including what equations and/or principles of physics you are using.
v0x = ?
v0y = ?
Y
X
h = 1470 m
valley
d = 2940 m
v0x of Cannonball = _________________________________________ m/s
v0y of Cannonball = _________________________________________ m/s
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Name _______________________________________________________________________
Problem C-2 (32 Points) – Colliding Objects (Questions Page)
Please put your answers to this problem on the next page.
Consider the following situation: Two objects, each with mass = 500 g, are sliding on frictionless
ice. Object A is moving at 16.0 m/s in the +X direction and Object B is moving at 12.0 m/s in
the +Y direction. They are made of magnetic material and they stick together when they collide.
After the collision, they continue sliding on the frictionless ice together.
Y
Object A
16.0 m/s
X
12.0 m/s
Object B
C-2-1: State in a few complete sentences the Impulse-Momentum Theorem and indicate in your
answer which equation on the formula sheet best expresses this theorem.
C-2-2: Does the Principle of Conservation of Momentum apply to this problem? Explain why or
why not in a few complete sentences. Indicate in your answer what you selected as your system
and why.
C-2-3: What was the total impulse (X and Y components) on Object A during the collision?
(You can use the remainder of this page for scratch work.)
6
Name _______________________________________________________________________
Problem C-2 (32 Points) – Colliding Objects (Answers Page)
Please put your answers on this page.
Make sure you answer C-2-1, C-2-2, and C-2-3.
Show all work, including what equations and/or principles of physics you are using.
7
Name _______________________________________________________________________
Formula Sheet for Homework and Exams – Page 1 of 2


U    Fcons  dx
1.
v f  v 0  a t f  t 0 
23.
2.
x f  x 0  v 0 ( t f  t 0 )  12 a ( t f  t 0 ) 2
24.
U g  m g (y  y 0 )
3.
x f  x 0  ( v 0  v f )( t f  t 0 )
25.
U s  12 k ( x  x 0 ) 2
4.
x f  x 0  v f ( t  t 0 )  12 a ( t f  t 0 ) 2
26.
27.
28.
 K   U  Wnoncons
s  r
v tangential   r
29.
a tangential   r
5.
6.
1
2
v f  v 02  2ax f  x 0 
 

 F  Fnet  m a
2
7.
2r
T
v
8.
a centripetal 
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
v2
 2 r
r
a radial  a centripetal


p  mv

 
dp
 F  Fnet  d t



J   Fnet dt   p


P   pi


dP
  Fext
dt
30.
  0  t  t 0 
31.
   0  0 ( t  t 0 )  12 ( t  t 0 ) 2
32.
   0  12 (0  )( t  t 0 )
33.
   0  ( t  t 0 )  12 ( t  t 0 ) 2
 2  02  2   0 
   
35a. a  b  a b sin( )
 
a  b  a y b z  a z b y î 
35b.
a z b x  a x b z  ĵ  a x b y  a y b x k̂
34.

36.
37.
M   mi
38.
1
1
x cm   m i x i y cm   m i y i
M
M


P  M v cm
   
a  b  a b cos()  a x b x  a y b y  a z b z
 
W  Fd
 
W   F  dx
21.
K  12 m v 2  12 m (v x  v y )
22.
K f  K i  Wnet
2
39.
40.
41.
42.
43.
2
I   m i ri


2
K rot  12 I  2
 
W     d
  
  r F

 dL

  I  d t
  
l  r p


L  l i


L  I
44x. m1 v1, x ,before  m 2 v 2, x ,before  m1 v1, x ,after  m 2 v 2, x ,after
44y. m1 v1, y ,before  m 2 v 2, y ,before  m1 v1, y ,after  m 2 v 2, y,after
44z. m1 v1,z ,before  m 2 v 2,z ,before  m1 v1,z ,after  m 2 v 2,z ,after
45a. v1,f 
m1  m 2
2 m2
v1,i 
v 2 ,i
m1  m 2
m1  m 2
45b.
8
v 2,f 
2 m1
m  m1
v1,i  2
v 2 ,i
m1  m 2
m1  m 2

Formula Sheet for Homework and Exams – Page 2 of 2
46a.
46b.
47a.
47b.
48a.
48b.
49.

m m
| F | G 1 2 2
r

m m
F  G 1 2 2 r̂
r

1 | q1 || q 2 |
| F |
4  0
r2

1 q1 q 2
F
(r̂ )
4  0 r 2

1 | qi |
| Ei |
4   0 ri 2

1 qi
E
(r̂i )
4   0 ri 2


F  qE
50.
51.
52.
1 qi
4   0 ri
U  qV
 
V    E  dx
V
V
x
V
53y. E y  
y
V
53z. E z  
z

 
54. F  q v  B
mv
55. r 
qB
53x. E x  
Useful Constants
(You can use the approximate values on exams.)
Universal Gravitation Constant
G  6.67310 11 N m 2 kg 2  6.67 10 11
Electrostatic Force Constant
1
 8.987551788 10 9 N m 2 C  2  9.0 10 9
4  0
Magnetic Constant
 0  4  10 7 H m 1  1.26 10 6
Speed of Light in Vacuum
c  2.99792458 10 8 m s 1  3.0 10 8
Charge of a Proton
e  1.602176462 10 19 C  1.6 10 19
Electron-Volt Conversion Constant
1eV  1.602176462 10 19 J  1.6 10 19
Mass of a Proton
m p  1.6726215810 27 kg  1.67 10 27
Mass of an Electron
m e  9.10938188 10 31 kg  9.110 31
9