Physics 221.
Exam I
Spring 2003
2. The Concorde cruises at 1450 mi/h (about twice the speed of sound). What is the cruise speed of
the Concorde in m/s? (1mile = 1609m)
a.
b.
c.
d.
e.
190 m/s
325 m/s
534 m/s
648 m/s
789 m/s
3. Let A = 3i + 4j + αk and B = 3i + 4j − αk. Which of the values of α given below makes A and B
perpendicular to each other?
a.
b.
c.
d.
e.
α=3
α = −3
α=4
α = −4
α=5
4. Two vectors A and B are drawn from a common point and C=A+B. If C2=A2+B2, the angle
between A and B is:
a. 0°
b. 15°
c. 30°
d. 90°
e. 120°
Page 1 of 12
Physics 221.
Exam I
Spring 2003
5. The motion of a car traveling in a straight line has been photographed at regular intervals of time.
The diagram below shows the positions of the car at t = 1s, t = 2s, etc. The positive x-axis is taken as
shown in the figure.
t=1s
t=2s
t=3s
t=4s
t=5s t=6s
x
Which of the following diagrams is a reasonable description of the motion of this car? (Note that two
of the diagrams are distance vs. time x(t) and the other three are velocity in the x-direction vs. time
v(t))
x
3s
6s
t
B
A
v
v
3s
C
6s
t
3s
6s
t
D
v
3s
E
Page 2 of 12
6s
t
Physics 221.
Exam I
Spring 2003
6. A car is moving in a straight line. Its position x at time t is given by the equation x(t) = α t (β−t2),
where t is in seconds, α = 3.0 m/s3 and β = 1.0 s2. At what time t is the acceleration instantaneously
zero?
a.
b.
c.
d.
e.
It is always zero.
It is never zero.
At t = 3.5 s
At t = 1 s
At t = 0 s
7. A subway train starts from rest at a station and accelerates at a rate of 1.6 m/s2 for 14 s. It then
runs at constant speed for 70 s and finally slows down at a rate of 3.5 m/s2 until it stops at the next
station. Find the total distance traveled.
a.
b.
c.
d.
e.
d = 760 m
d = 910 m
d = 1010 m
d = 1110 m
d = 1800 m.
8. A car moves from an initial position ri = (10 m) i + (20 m) j to a final position rf = (−20 m) i +
(60 m) j in a time interval of 5.0 s. The magnitude of the average velocity of the car during this
time interval is:
a.
b.
c.
d.
e.
5 m/s
10 m/s
15 m/s
20 m/s
25 m/s
Page 3 of 12
Physics 221.
Exam I
Spring 2003
9. A particle moves at constant speed along the trajectory shown below. Compare the magnitude of
the acceleration of the particle at points A and B.
A
a.
b.
c.
d.
e.
aA > aB ≠ 0
aA > aB = 0
aA < aB
aA = aB = 0
aA = aB ≠ 0
B
The situation below refers to the next two questions:
A particle moves with constant speed around the circle shown below. When it is at point A, its
coordinates are x = 0, y = 2 m and its velocity is v = (4 m/s) i.
10. When it is at point B, its acceleration aB is:
y
A
B
x
a.
b.
c.
d.
e.
aB = 2 m/s2 i
aB = 4 m/s2 i
aB = 8 m/s2 i
aB = 4 m/s2 j
aB = –8 m/s2 j
11. The period of the motion of this particle is:
a.
b.
c.
d.
e.
T = 0.3 s
T = 1.6 s
T = 3.1 s
T = 4.5 s
T = 5.1 s
Page 4 of 12
Physics 221.
Exam I
Spring 2003
12. A particle moves along a circular path of radius R = 20 cm. Its speed is decreasing at a constant
rate. Its speed at t = 0 is 25 cm/s. At t = 4 s, the speed is 10 cm/s. What is the magnitude of the
acceleration of the particle at t = 4 s?
a.
b.
c.
d.
e.
a = 1.2 cm/s2
a = 3.8 cm/s2
a = 5.0 cm/s2
a = 6.3 cm/s2
a = 8.8 cm/s2
13. Which of the graphs below best represents the vertical component of velocity versus time for a
projectile fired at an angle of 45° above the horizontal?
vvvyy
y
ttt
C
A
B
vy
t
E
D
Page 5 of 12
Physics 221.
Exam I
Spring 2003
The situation below refers to the next two questions:
A person stands on top of a building and throws a baseball off the building from a height
20 m above the ground at a speed of 40 m/s and an angle of 30° above the horizontal. Neglect air
resistance and use g = 10 m/s2.
14. The maximum height above the ground the ball can reach is:
a.
b.
c.
d.
e.
hmax = 20 m
hmax = 40 m
hmax = 60 m
hmax = 80 m
hmax = 100 m
15. The time the ball can travel in the air before it hits the ground is:
a.
b
c.
d.
e.
2.8 s
4.5 s
4.8 s
6.2 s
8.5 s
Page 6 of 12
Physics 221.
Exam I
Spring 2003
16. A river flows due East with a speed of 3 m/s. The river is 800 m wide. The speed of the boat
relative to the water is 5 m/s. The boat must go to point P, located on the opposite bank directly
North of the starting point. How much time is required to reach point P?
a.
b.
c.
d.
e.
100 s
120 s
160 s
200 s
400 s
17. The figure below shows the strobe diagram of the motions of a rectangle and an oval in one
second intervals (1 indicates the position of each object at time 1 s, and so on). Assume the motion is
smooth.
1
2
3
4
LEFT
RIGHT
1
2
3
4
When observed from the reference frame of the rectangle, at t = 2 s the oval:
a.
b.
c.
d.
e.
Is momentarily at rest.
Is moving to the left and slowing down.
Is moving to the left and speeding up.
Is moving to the right and slowing down.
Is moving to the right and speeding up.
Page 7 of 12
Physics 221.
Exam I
Spring 2003
18. An object of mass m = 2 kg is at rest at t = 0. A force F = (6 i + 8 t3 j), in Newtons, is exerted on
it. What is the velocity of the object at the time t = 1 s?
a.
b.
c.
d.
e.
v(t = 1 s) = (24 j) m/s
v(t = 1 s) = (3 i + j) m/s
v(t = 1 s) = (6 i + 2 j) m/s
v(t = 1 s) = (6 i + 8 j) m/s
v(t = 1 s) = (5 i + 2 j) m/s
19. Four blocks of masses m1 = 1 kg, m2 = 2 kg, m3 = 3 kg and m4 = 4 kg are on a frictionless
horizontal surface as shown on the figure below. The blocks are connected by ideal massless strings.
A force FL = 30N is applied to the left block, and is directed to the left. Another force FR = 50N is
applied to the right block, and is directed to the right. What is the magnitude of the tension T in the
string between m2 and m3?
FL = 30N
a.
b.
c.
d.
e.
m1 = 1kg
m2 = 2 kg
T
FR = 50N
m3 = 3 kg
m4 = 4 kg
T=6N
T = 20 N
T = 30 N
T = 36 N
T = 50 N
20. A sphere of mass 2.0 × 10−4 kg is suspended from an ideal, massless string. A steady horizontal
breeze pushes the sphere so that the cord makes a constant angle of 60° with the vertical. Find T, the
tension on the string.
a.
b.
c.
d.
e.
T = 1.0 × 10−3 N
T = 1.7 × 10−3 N
T = 2.0 × 10−3 N
T = 2.9 × 10−3 N
T = 3.9 × 10−3 N
Page 8 of 12
Physics 221.
Exam I
Spring 2003
21. Two boxes of masses m and 4m are pushed together along a frictionless surface by a constant
force of magnitude N as shown in the figure. Let FL be the magnitude of the net force on large box
and FS the magnitude of the net force on the small box. Which of the following relation between
these magnitudes is true?
a.
a.
a.
a.
a.
FL < N, FS < N
FL > N, FS < N
FL > N, FS = N
FL = N, FS < N
FL = N, FS = N
4m
N
m
22. A person drops a quarter while standing on an elevator traveling upwards at a constant speed of
2 m/s. While the quarter is in the air, what is its acceleration?
a.
b.
c.
d.
e.
9.8 m/s2, direction down.
Less than 9.8 m/s2, direction down.
Less than 9.8 m/s2, direction up.
More than 9.8 m/s2, direction down.
0 m/s2
23. A kid takes a ride on a merry-go-round in the playground. If he moves at constant speed, which
of the black bold arrows in the figure is a good option for the vector that represents the net force on
the kid?
B
C
D
A
Kid
Direction
of rotation
a.
b.
c.
d.
e.
A
B
C
D
E
E
Page 9 of 12
View from above
Physics 221.
Exam I
Spring 2003
The situation below refers to the next two questions:
A child drags her teddy bear by one arm as shown in the figure below, moving to the right along a
straight line at a constant speed of 0.75 m/s. The force exerted by the child is F = 8.0 N and forms an
angle θ = 30° with the horizontal. The mass of the teddy is m = 1.2 kg.
F
θ
24. Find the magnitude of the frictional force between the floor and the teddy.
a. Ff
b. Ff
c. Ff
d. Ff
e. Ff
= 3.5 N
= 4.0 N
= 5.3 N
= 6.9 N
= 8.8 N
25. The magnitude of the normal force exerted by the floor on the teddy is:
a.
b.
c.
d.
e.
N = 4.0 N
N = 7.8 N
N = 9.2 N
N = 11.8 N
N = 14.1 N
Page 10 of 12
Physics 221.
Exam I
Spring 2003
The situation below refers to the next three questions:
A box with mass m sits on an incline. The plane of the incline makes an angle θ with the horizontal.
The coefficients of static and kinetic friction between the box and the plane are µs = 0.40 and µk =
0.20, respectively.
m
θ
26. Find the maximum value of θ for which the box can sit motionless on the incline without sliding
down.
a.
b.
c.
d.
e.
θ = 9°
θ = 11°
θ = 15°
θ = 22°
θ = 29°
27. For θ = 30°, find the magnitude of the acceleration of the box.
a.
b.
c.
d.
e.
a = 1.4 m/s2
a = 3.2 m/s2
a = 4.9 m/s2
a = 6.7 m/s2
a = 9.8 m/s2
28. Which of the arrows in the figure below is a good option to describe the total force exerted by
the box on the incline?
A
m
B
a.
b.
c.
d.
e.
E
C
D
A
B
C
D
E
θ
Page 11 of 12
Physics 221.
Exam I
Spring 2003
The situation below refers to the next two questions:
Three boxes with masses m1, m2 and m3 are connected with two ideal cables and placed as shown in
the figure below. The cable between m2 and m3 goes through an ideal pulley.
m1
m2
m3
29. If m1 is increased, the magnitude of the acceleration of m3:
a.
b.
c.
d.
e.
Decreases only if the friction between the table and m1 is not negligible.
Decreases, independently of friction.
Stays the same. (independently of friction).
Increases only if the friction between the table and m1 is not negligible.
Increases, independently of friction.
30. Proposition: The magnitude of the force that m1 exerts on m2 is equal to the magnitude of the
force that m2 exerts on m1. Is this true?
a.
b.
c.
d.
e.
Only when m2 = m1.
Only when the acceleration is zero.
Only when the system is at rest.
Only when friction with the table is negligible.
Yes, it’s true.
Did you bubble in your exam version and
your registration number?
Page 12 of 12