Download Exam 2

Name: ________________________ Class: ___________________ Date: __________
ID: A
Exam 2--PHYS 101--F15
Multiple Choice
Identify the choice that best completes the statement or answers the question.
#27 is a bonus question. It is worth 3 points. Write your answer to the question on the form in the designated area.
1. A projectile is fired at 25o above the horizontal.
3. A spring loaded gun shoots a ball in the horizontal
direction from a height of 20.0 m. The ball travels
3.0 m. What is its initial velocity?
At the highest point in its trajectory, its speed is
100 m/s. If air resistance is ignored, the initial
velocity had a horizontal component of
a. 100 m/s.
b. 100/sin(25o) m/s.
c. 100 sin(25o) m/s.
d. 0 m/s.
e. 100 cos(25o) m/s.
2. A large cannon is fired from ground level over
level ground at an angle of 60° above the
horizontal. The muzzle speed is 100 m/s.
Neglecting air resistance, what maximum height
will the projectile reach?
a.
b.
c.
d.
-10 m/s
1.5 m/s
3.2 m/s
6.7 m/s
4. For the two-dimensional motion of a projectile
a.
b.
c.
d.
e.
that begins and ends at the same height, all of
the following apply except
a. the maximum height occurs at the midpoint
of the flight.
b. the time of flight to half the maximum
height is equal to 1/4 the total time of
flight.
c. the path is a parabola.
d. the maximum range occurs when the launch
angle is 45°.
400 m
800 m
100 m
900 m
1000 m
1
Name: ________________________
ID: A
5. A stone is thrown horizontally and follows the path
XYZ shown. The direction of the velocity of the
stone at point Y is shown by which of the vectors
A-E?
8. Two shells are fired simultaneously from the
same battleship at two targets. The shells
follow the trajectories shown here. Which
target will be hit first?
a.
b.
a.
b.
c.
d.
e.
c.
d.
A
B
C
D
E
Target 1
More information is needed to work out the
answer.
Both targets will be hit at the same time.
Target 2
9. An object is moving at constant velocity.
Which statement is always true?
a. There must be more than one force acting
on the object.
b. There is only one force acting on the object.
c. There are no forces acting on the object.
d. The net force on the object is zero.
6. A basketball is shot from a free-throw range.
At the top of the basketball’s trajectory, its
acceleration is
a. more than the acceleration due to gravity.
b. unknown; more information is needed to
work out the answer.
c. less than the acceleration due to gravity.
d. equal to the acceleration due to gravity.
e. zero.
10. An object is dropped out of an airplane. It falls
and eventually reaches a constant speed
(terminal velocity). After the object reaches
terminal velocity, which of the following
statements is true?
a. The force of air resistance is zero.
b. The acceleration of the object is equal to g.
c. The force of air resistance is equal to the
weight of the object.
d. There are no forces acting on the object.
7. A pilot drops a package of food and water
supplies from a plane that is flying horizontally
at constant speed. When the package reaches
the ground, the plane’s horizontal position
relative to the package
a. is unknown; more information is needed to
work out the answer.
b. is behind the package.
c. is directly above the package.
d. depends on the mass of the package.
e. is in front of the package.
11. The fact that a dime pulls upward on the Earth
with a force equal to the weight of the dime is
an example of
a. Newton’s first law.
b. Newton’s second law.
c. Newton’s third law.
d. none of the above.
2
Name: ________________________
ID: A
12. An 80-kg person falls out of an airplane and
15. A 500-N force is required to accelerate a car
eventually reaches maximum speed (terminal
velocity). We estimate the force of air friction
at this speed to be
a.
b.
c.
d.
from rest to 3.9 m/s in 12 seconds. We estimate
the mass of the car to be
0 N.
22 N.
800 N.
52 N.
a.
b.
c.
d.
13. Two objects, A and B, experience the same net
force. Object A accelerates at twice the rate of
object B. Therefore the
a. mass of A is four times that of the mass of
B.
b. mass of A is half that of the mass of B.
c. mass of A is twice that of the mass of B.
d. mass of A is one-quarter that of the mass of
B.
16. A woman who weighs 700 N steps onto a scale
that is in an elevator. The elevator begins to
accelerate. The woman now weighs 500 N
(according to the scale). The acceleration of the
elevator is
14. A block with mass 1.0 kg sits on the floor. A force
of 5 N is required to move the block. What is the
coefficient of static friction?
a.
b.
c.
d.
a.
b.
c.
d.
5000 kg.
1500 kg.
2500 kg.
4500 kg.
0.1
0.05
0.5
0.2
3
2
4.2 m/s
2
2.9 m/s
2
2.9 m/s
2
4.2 m/s
downward.
downward.
upward.
upward.
Name: ________________________
ID: A
17. A 5-kg mass is pulled up a smooth incline at a
constant speed by a rope. The rope is parallel
with the surface of the incline. If the incline is
50° relative to the horizontal, the tension in the
rope is
a.
b.
c.
d.
38 N.
44 N.
41 N.
49 N.
18. Consider this figure. The block is stationary; static friction is holding it on the plane. Which of the following
equations is correct?
I. F w cos 60 − f s = 0
II. F w − F N = ma
III. F w cos 60 = ma x
IV. F w sin60 = F N
a.
b.
I & IV
none are correct
c.
d.
IV only
I, II, and III
4
Name: ________________________
ID: A
21. Consider a block that is at rest on an inclined plane.
The only forces acting on the block are the
frictional, normal, and gravitational forces. Which
of these statements best describe the normal force
acting on the block?
a. N>mg
b. N<mg
c. N=mg
d. it depends on the weight of the block
19. An 8-kg mass is pulled across a smooth floor
using a rope. The rope makes an angle of 28°
with the floor. If the tension in the rope is 45 N,
the acceleration of the 8-kg mass is
22. A 2-kg object is moving at 3m/s. A 4-N force is
applied in the direction of motion and then
removed after the object has traveled an additional
5m. The work done by this force is:
a.
b.
c.
d.
2
7.2 m/s .
5.0 m/s 2 .
2
6.2 m/s .
2
7.8 m/s .
a.
b.
c.
d.
e.
20. A 5.5-kg object, moving at constant velocity, is
23. A car travels a distance x at acceleration a and does
work W. If the car travels a distance 2x at the same
acceleration, what is the work it has done?
acted on by three forces. One force is 20 N
along the +x axis. The second force is 25 N
along the +y axis. What is the magnitude of the
third force? (Hint: The object is not
accelerating. What is the net force?)
a.
b.
c.
d.
15 J
12 J
18 J
20 J
38 J
a.
b.
c.
d.
35 N
28 N
32 N
23 N
5
W
W
2W
4W
Name: ________________________
ID: A
26. A guy pulls a block 5.0 m across the floor as shown
here. What work is done?
24. These four blocks are all moving to the right.
Which of the forces is doing zero work on the
block?
a.
b.
c.
d.
e.
a
b
c
d
more than one is doing zero work
a.
b.
c.
d.
25. Which of these is the basic SI unit for work?
2
a.
b.
c.
d.
130 J
500 J
150 J
75 J
m kg
s
m2 kg
s2
kg m
s
m kg
s2
Problem
27. (Extra credit; record your answer on the form.) A Nicholls soccer player kicks a ball with an initial speed of 20.0
m/s (50 mph) at some angle from the horizontal. The ball travels a horizontal distance of 39.5 m in 2.58 seconds.
What is the maximum height of the ball?
6
ID: A
Exam 2--PHYS 101--F15
Answer Section
MULTIPLE CHOICE
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
21.
22.
23.
24.
25.
26.
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
A
A
B
B
B
D
C
A
D
C
C
C
B
C
B
B
A
A
B
C
B
D
C
A
B
D
PTS:
PTS:
PTS:
PTS:
PTS:
PTS:
PTS:
PTS:
PTS:
PTS:
PTS:
PTS:
PTS:
PTS:
PTS:
PTS:
PTS:
PTS:
PTS:
PTS:
PTS:
PTS:
PTS:
PTS:
PTS:
PTS:
1
1
1
0
1
0
0
1
0
1
1
1
1
1
1
1
0
1
0
0
1
1
1
1
1
1
REF:
REF:
REF:
REF:
F15-both
F14 Final
F15
F15
REF:
REF:
REF:
REF:
REF:
REF:
REF:
REF:
REF:
REF:
REF:
REF:
F15
F15
F15
F15
F15
F15
F15
F15
F15
F15
F15
F15
REF:
REF:
REF:
REF:
F15
F15
F15
F15
REF: F15
REF: F15
PROBLEM
27. ANS:
8.26 m
PTS: 1
1