PHYSICS 221
Summer 2007
EXAM 1: June 25 2007 9:50am—10:50am
Name (printed): ______________________________________________
Recitation Instructor: _________________________
Section #_______
INSTRUCTIONS:
This exam contains 13 equally weighted multiple-choice questions. Choose one answer only
for each question. Choose the best answer to each question. Answer all questions.
Allowed material: Before turning over this page, put away all materials except for pens, pencils,
erasers, rulers, your calculator. There is a formula sheet attached at the end of the exam. Other
copies of the formula sheet are not allowed.
Calculator: In general, any calculator, including calculators that perform graphing numerical
analysis functions, is permitted. Electronic devices that can store large amounts of text, data or
equations are NOT permitted. If you are unsure whether or not your calculator is allowed for the
exam, ask your TA.
Examples of electronic devices that are not permitted: Any laptop, palmtop, pocket
computer, PDA or e-book reader.
How to fill in the bubble sheet:
Use a number 2 pencil. Do NOT use ink. If you did not bring a pencil, ask for one.
Write and fill in the bubbles corresponding to:
- Your last name, middle initial, and first name.
-   Your ID number (the middle 9 digits on your ISU card)  
- Special codes K to L are your recitation section. (01, 02, 03)
Please turn over your bubble sheet when you are not writing on it.
If you need to change any entry, you must completely erase your previous entry. Also, circle
your answers on this exam booklet. Before handing in your exam, be sure that your answers
on your bubble sheet are what you intend them to be. You may also copy down your answers on
a piece of paper to take with you and compare with the posted answers. You may use the table at
the end of the exam for this.
When you are finished with the exam, place all exam materials, including the bubble sheet, and
the exam itself, in your folder and return the folder to your instructor.
No cell phone calls allowed. Either turn off your cell phone or leave it at home. Anyone
answering a cell phone must hand in their work; their exam is over.
Best of luck, Paula Herrera.
The situation shown below refers to the next two problems:
A toy chest and its contents have a combined weight of 180 N. A child moves it at
constant speed across the floor of a 10-m long hallway by pulling with a tension of
100 N on an attached rope that makes an angle of 30° with the horizontal.
1. Determine the coefficient of kinetic friction between the chest and the floor.
a.
b.
c.
d.
e.
0.12
0.38
0.48
0.67
0.92
2. What is the work done by the tension on the chest?
a.
b.
c.
d.
e.
0
320 J
500 J
870 J
1000 J
3. Consider the vectors in the figure below:
A
B
C
D
Which of the following is true?
a.
b.
c.
d.
e.
G G
A⋅C < 0
G G G G
A⋅C = D ⋅ B
G G G G
A× C = D × B
G G G G
A× C = C × A
G G
C⋅D = 0
4. At t = 0, a 3.0-g particle is at the origin and has a velocity vx = −4.0 m/s . The
acceleration of the particle is ax (t ) = ( 3.0 m/s3 ) t , where t is the time in seconds.
What is the position of the particle at t = 4.0 s?
a.
b.
c.
d.
e.
x = 12 m
x = 16 m
x = 80 m
x = 120 m
x = 180 m
5. A bead of mass m is threaded on a wire in the shape of a vertical circle of radius
R. The bead is placed at the highest point of the circle and given a very tiny push
so that it slides down (see figure). What is the work by gravity as the bead moves
from the top to the bottom of the circle?
bead
a.
b.
c.
d.
e.
−2Rmg
− Rmg
0
Rmg
2Rmg
R
g
6. A rotating fan completes 1200 revolutions every minute. What is the magnitude
of the acceleration of the tip of the blade, at a radius of 0.150 m?
a.
b.
c.
d.
e.
0
0.17 m/s2
66 m/s2
2370 m/s2
216000 m/s2
7. A particle moves at constant speed along the trajectory shown below.
A
●
N
E
W
●
B
S
Which of the following best describes the direction and magnitude of the acceleration of
the particle at points A and B?
a.
b.
c.
d.
e.
aA = aB = 0
aA = aB ≠ 0, both pointing south
aA < aB, both pointing south
aA = aB ≠ 0, aA pointing south, aB pointing north,
None of the above.
8. Snow is falling vertically at a constant speed of 8.0 m/s. At what angle from the
vertical do the snowflakes appear to be falling as viewed by the driver of a car
traveling on a straight, level road with a speed of 50 km/h?
a.
b.
c.
d.
e.
0°
9°
30°
60°
81°
The situation shown below refers to the next two problems:
A skier starts from rest at the top of a ramp (point A), slides down and jumps off at
the end of the ramp (point B), landing in the plain at the bottom (see figure). The end
of the ramp is at a height of 30 m above the plain. When the skier leaves the ramp, he
is moving at 30 m/s at an angle of 30° above the horizontal. Neglect friction and air
resistance.
9. How high h above the plain is the top of the ramp?
a.
b.
c.
d.
e.
h = 46 m
h = 62 m
h = 76 m
h = 85 m
h = 90 m
●
A
B
●
h
30 m
plain
10. How long is the skier in the air, after leaving the ramp?
a.
b.
c.
d.
e.
2.1 s
4.4 s
6.0 s
7.0 s
8.6 s
11. A 1.0-kg block is held at rest on an incline with angle 20° with the horizontal. The
coefficients of friction between the block and the incline are µS = 0.50 and µk =
0.30. What is the acceleration of the block after it is released?
a.
b.
c.
d.
e.
0
0.59 m/s2
1.3 m/s2
3.4 m/s2
9.8 m/s2
12. Two blocks with masses 2.0 kg and 4.0 kg are stacked on a horizontal, frictionless
surface. A horizontal force F = 12 N is applied on the top block (see figure) and
both blocks are observed to move together.
2.0 kg
12 N
4.0 kg
What is the magnitude of the friction force between the two blocks?
a.
b.
c.
d.
e.
2.0 N
3.0 N
4.0 N
8.0 N
Cannot say because the coefficients of friction are not given.
13. A bead of mass m at the end of a massless, ideal string of length l moves in
horizontal circles at constant speed as shown below (conical pendulum). What is
the direction of the net force on the bead?
θ
l
A
D
B
C
a.
b.
c.
d.
e.
Vector A (along the string)
Vector B (toward the center of the circle)
Vector C (toward the center of the circle and down)
Vector D (outward from the center of the circle)
None of the above.
Here you can write down your answers and keep this page to compare with the posted
solutions.
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