Download Physics Semester Exam Study Guide January 2013 Answer Section

Physics Semester Exam Study Guide January 2013
Short Answer (2 points)
1. Distinguish between the displacement of a traveler who takes a train from New York to Boston and the
displacement of a traveler who flies from Boston to New York.
2. Two objects move separately after colliding, and both the total momentum and total kinetic energy remain
constant. Identify the type of collision.
3. Which would fall with greater acceleration in a vacuum—a leaf or a stone?
4. Ball A has triple the mass and speed of ball B. What is the ratio of the kinetic energy of ball A to ball B.
5. Which of the following equations best describes the graph above?
6. What is the path of a projectile (in the absence of friction)?
7. Which of the following is the cause of an acceleration?
8. What form of energy is associated with the position of an object in Earth’s gravitational field?
9. Two swimmers relax close together on air mattresses in a pool. One swimmer’s mass is 48 kg, and the other’s
mass is 55 kg. If the swimmers push away from each other,
10. The magnitude of the gravitational force acting on an object is
11. What are the SI units for momentum?
12. In the figure above, which diagram represents the vector subtraction C = A–B?
13. A child pulls a toy across the floor. Is the work done on the toy positive, negative, or zero?
14. Which of the following situations represents a negative displacement? (Assume positive position is measured
vertically upward along a y-axis.)
15. A crate is carried in a pickup truck traveling horizontally at 15.0 m/s. The truck applies the brakes for a distance
of 28.7 m while stopping with uniform acceleration. What is the coefficient of static friction between the crate and
the truck bed if the crate does not slide?
16. When a car’s velocity is negative and its acceleration is negative, what is happening to the car’s motion?
17. The change in an object’s momentum is equal to
18. A net force of 6.8 N accelerates a 31 kg scooter across a level parking lot. What is the magnitude of the scooter’s
acceleration?
19. What term is used to describe the vector sum of all the forces acting on an object?
20. Acceleration is defined as
21. A passenger on a bus moving east sees a man standing on a curb. From the passenger’s perspective, the man
appears to
22. A child pulls a balloon for 12 m with a force of 1.0 N at an angle 60 below horizontal. How much work does the
child do on the balloon?
23. A soccer ball collides with another soccer ball at rest. The total momentum of the balls
24. Which of the following is the rate at which work is done?
25. A newton is equivalent to which of the following quantities?
26. Suppose you are given a position versus time graph. The slope of a line drawn tangent to a point on the curve of
this graph describes what quantity?
27. The Greek letter  (delta) indicates a(n)
28. An ant on a picnic table travels 3.0  10 cm eastward, then 25 cm northward, and finally 15 cm westward. What
is the magnitude of the ant’s displacement relative to its original position?
29. How much power is required to lift a 2.0 kg mass at a speed of 2.0 m/s?
30. Acceleration due to gravity is also called
31. Which of the following is the motion of objects moving in two dimensions under the influence of gravity?
32. What quantity is the sum of the kinetic energy and all forms of potential energy in a system?
33. What two dimensions, in addition to mass, are commonly used by physicists to derive additional measurements?
34. How many displacement vectors shown in the figure above have horizontal components?
35. How many displacement vectors shown in the figure above have components that lie along the y-axis and are
pointed in the –y direction?
36. A child moving at constant velocity carries a 2 N ice-cream cone 1 m across a level surface. What is the net work
done on the ice-cream cone?
37. A 3.00 kg toy falls from a height of 1.00 m. What will the kinetic energy of the toy be just before the toy hits the
ground? (Assume no air resistance and that g = 9.81 m/s .)
38. A measure of the quantity of matter is
39. Work is done when
40. What is the potential energy of a 1.0 kg mass 1.0 m above the ground?
41. If two teams playing tug-of-war pull on a rope with equal but opposite forces, what is the net external force on the
rope?
42. A late traveler rushes to catch a plane, pulling a suitcase with a force directed 30.0 above the horizontal. If the
horizontal component of the force on the suitcase is 60.6 N, what is the force exerted on the handle?
The figure above shows the path of a ball tossed from a building. Air resistance is ignored.
43. In the figure above, the horizontal component of the ball’s velocity at A is
44. In the figure above, the magnitude of the ball’s velocity is greatest at location
45. At what point of the ball’s path shown in the figure above is the vertical component of the ball’s velocity zero?
46. In the figure above, at which point is the ball’s speed about equal to the speed at which it was tossed?
47. What quantity describes the difference between an object’s initial position and the object’s final position?
48. For an object to be in equilibrium, the net force acting on the object must have what value?
49. Which of the following is a true statement about the conservation of energy?
50. According to the graph above, during which interval is the cat at rest?
51. According to the graph above, during which interval does the cat have the greatest positive velocity?
52. After colliding, objects are deformed and lose some kinetic energy. Identify the type of collision.
53. The free-body diagram shown above represents a car being pulled by a towing cable. In the diagram, the 5800 N
force is
54. Which of the following is a physical quantity that has both magnitude and direction?
55. A roller coaster climbs up a hill at 4 m/s and then zips down the hill at 30 m/s. The momentum of the roller
coaster
56. Which form of energy is involved in weighing fruit on a spring scale?
57. Which of the following is an area of physics that studies motion and its causes?
58. What is a term for the quantity Ft, where F is an applied force and t is the time interval over which the force is
applied?
59. Which are simultaneous equal but opposite forces resulting from the interaction of two objects?
60. A baseball catcher throws a ball vertically upward and catches it in the same spot as it returns to the mitt. At what
point in the ball’s path does it experience zero velocity and nonzero acceleration at the same time?
Problem - Choose 15 problems. NO work = NO credit ( 3points each)
A 68.0 kg diver jumps off a diving platform, rises about 1 m above the platform, then falls to the pool.
61. The diver strikes the water at a speed of 14.7 m/s, then slows to a stop underwater in 0.35 s. What force does the
water exert on the diver?
62. A quarterback takes the ball from the line of scrimmage and runs backward for 1.0  10 m. He then runs
sideways, parallel to the line of scrimmage, for 15 m. Next, he throws the ball forward 5.0  10 m, perpendicular
to the line of scrimmage. The receiver is tackled immediately. How far is the football displaced from its original
position?
63. A boat moves at 10.00 m/s relative to the water. If the boat is in a river where the current is 2.00 m/s, how long
does it take the boat to make a complete round trip of 1000.0 m upstream followed by 1000.0 m downstream?
64. An Olympic skier moving at 20.0 m/s down a 30.0 slope encounters a region of wet snow and slides 145 m
before coming to a halt. What is the coefficient of friction between the skis and the snow? (g = 9.81 m/s2)
65. Two cars pass each other traveling at the same speed. One car has a constant velocity of 15.0 m/s, east. The other
car has a constant acceleration of 1.00 m/s , west. How much time will have elapsed until the cars are 164 m
apart?
66. Water flows over a section of Niagara Falls at a rate of 1.50  10 kg/s and falls 70.0 m. What is the power of the
waterfall?
67. A worker pushes a box with a horizontal force of 50.0 N over a level distance of 5.0 m. If a frictional force of 43
N acts on the box in a direction opposite to that of the worker, what net work is done on the box?
68. A waitperson pushes the bottom of a glass tumbler full of water across a tabletop at constant speed. The tumbler
and its contents have a mass of 0.70 kg, and the coefficient of kinetic friction for the surfaces in contact is 0.41.
What force does the waitperson exert on the glass? g = 9.81 m/s )
69. Experiencing a constant horizontal 1.10 m/s wind, a hot-air balloon ascends from the launch site at a constant
vertical speed of 2.50 m/s. At a height of 205 m, the balloonist maintains constant altitude for 10.0 s before
releasing a small sandbag. How far from the launch site does the sandbag land?
70. A stone is thrown at an angle of 30.0 above the horizontal from the top edge of a cliff with an initial speed of 12
m/s. A stopwatch measures the stone’s trajectory time from the top of the cliff to the bottom at 5.60 s. What is the
height of the cliff? (Assume no air resistance and that a = g = 9.81 m/s .)
71. An elevator weighing
N is supported by a steel cable. What is the tension in the cable when the
elevator is accelerated upward at a rate of 6.00 m/s ? (g = 9.81 m/s )
72. A 16.0 kg child on roller skates, initially at rest, rolls 2.0 m down an incline at an angle of 20.0 with the
horizontal. If there is no friction between incline and skates, what is the kinetic energy of the child at the bottom
of the incline? (g = 9.81 m/s )
73. A jet engine develops 1.0  10 N of thrust to move an airplane forward at a speed of 9.0  10 km/h. What is
the power output of the engine?
74. A warehouse worker pulls on the handles of a 96.0 kg cart with a net force of 128 N an angle of 55.0 above the
horizontal. Attached to the cart is a smaller cart having a mass of 72.0 kg. What is the magnitude of the horizontal
acceleration of the less massive cart?
75. A plane flies from city A to city B. City B is 1540 km west and 1160 km south of city A. What is the total
displacement of the plane?
76. A swimmer with a mass of 95 kg dives off a raft with a mass of 300 kg. If the swimmer’s speed is 5 m/s
immediately after leaving the raft, what is the speed of the raft?
77. A hill is 150 m long and makes an angle of 18 with the horizontal. As a 58 kg jogger runs up the hill, how much
work does the jogger do against gravity?
78. A baseball bat strikes a baseball with a force of 45 N. The bat is in contact with the ball for 0.22 s. What is the
magnitude of the change in momentum of the ball?
79. A 48.0 N crate starting at rest slides down a rough 7.0 m long ramp inclined at 40.0 with the horizontal. The
force of friction between the crate and ramp is 6.0 N. Using the work-kinetic energy theorem, find the velocity of
the crate at the bottom of the incline.
80. A rock is thrown downward from the top of a cliff with an initial speed of 22 m/s. If the rock hits the ground after
2.8 s, what is the height of the cliff? (Disregard air resistance. a = g = 9.81 m/s .)
81. While grazing, a caribou treks 225 m at 30.0west of south, and then 15 m west. What is the caribou’s resultant
displacement?
82. A kitten pushes a ball of yarn rolling toward it at 1.00 cm/s with its nose, displacing the ball of yarn 17.5 cm in
the opposite direction in 2.00 s. What is the acceleration of the ball of yarn?
83. Someone throws a rubber ball vertically upward from the roof of a building 9.00 m in height. The ball rises, then
falls. It just misses the edge of the roof, and strikes the ground. If the ball is in the air for 4.00 s, what was its
initial velocity? (Disregard air resistance. a = g = 9.81 m/s .)
84. A coin released at rest from the top of a tower hits the ground after falling 1.9 s. What is the speed of the coin as it
hits the ground? (Disregard air resistance. a = g = 9.81 m/s .)
85. A sled is pulled at a constant velocity across a horizontal snow surface. If a force of 8.0  10 N is being applied
to the sled rope at an angle of 53 to the ground, what is the magnitude of the force of friction of the snow acting
on the sled?
Physics Semester Exam Study Guide January 2013
Answer Section
SHORT ANSWER
1. The magnitudes of the displacements are equal, but the displacements are in opposite directions. Therefore,
one displacement is positive and one displacement is negative.
2. elastic
3. They would accelerate at the same rate.
4. 27
5. y =
x
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
a parabola
force
gravitational potential energy
their momenta are equal but opposite.
weight.
kgm/s
IV
positive
A cat jumps from a tree limb to the ground.
0.400
The car speeds up.
the product of the force applied to the object and the time interval.
18.
19.
20.
21.
22.
23.
24.
0.22 m/s
net force
the rate of change of velocity.
move west at a speed that is equal to the bus’s speed.
6.0 J
remains constant.
power
25.
26.
27.
28.
29.
30.
31.
32.
33.
34.
35.
36.
37.
38.
kgm/s
instantaneous velocity
difference or change.
29 cm
39 J
free-fall acceleration.
projectile motion
mechanical energy
length and time
4
2
0J
29.4 J
mass.
39.
40.
41.
42.
43.
44.
45.
46.
47.
48.
49.
50.
51.
52.
53.
54.
55.
56.
57.
58.
59.
60.
the displacement is not zero.
9.8 J
zero
70.0 N
equal to the horizontal component of its initial velocity.
D.
B
C
displacement
zero
Total energy is always conserved.
5.0–10.0 s
0.0–5.0 s
inelastic
the force exerted by the towing cable on the car.
vector
is greater down the hill than up the hill.
elastic potential energy
mechanics
impulse
action-reaction pairs
at the top of its path
PROBLEM
61. 2.9  10 N upward
Given
Solution
62. 43 m
Given
x = .0  10 m
y = 15 m
x = +5.0  10 m
Solution
63. 208 s
Given
vrg = velocity of river to ground = 2.00 m/s downstream
vbr = velocity of boat to river = 10.00 m/s
x = 1000.0 m downstream
x = 1000.0 m downstream
vbg = velocity of boat to ground
Solution
downstream
upstream
64. 0.415
Given:
vx,i = 20.0 m/s
x = 145 m
 = 30.0º
g = 9.81 m/s2
Solution
Choose a coordinate system such that the positive x-direction is down the ski slope. The force of friction will
be in the negative x-direction.
65. 5.0 s
Given
v =v = 15.0 m/s
a = 1.00 m/s
d = 164 m
Solution
66. 589 MW
Given
Solution
67. 35 J
Given
Solution
68. 2.8 N
Given
m = 0.70 kg
 = 0.41
g = 9.81 m/s
Solution
69. 108 m
Given
v = 1.10 m/s
v = 2.50 m/s
y = 205 m
y = 205 m
t = 10.0 s
Solution
70. 120 m
Given
v = 12 m/s at 30.0° above the horizontal
t = 5.60 s
g = 9.81 m/s
Solution
71. 2.61  10 N
Given
F =
g = 9.81 m/s
a = +3.00 m/s
Solution
72. 110 J
Given
N
Solution
73. 25 MW
Given
Solution
74. 0.437 m/s
Given
F
=128 N
 = 55.0
m = 96.0 kg
m = 72.0 kg
Solution
m
=m +m
75. 1930 km, 37.0° south of west
Given
d = 1540 km west
d = 1160 km south
Solution
76. 0.6 m/s
Given
Solution
77. 1  10 J
Given
Solution
78. 4.2 kgm/s
Given
Solution
79. 6.4 m/s
Given
Solution
80. 44 m
Given
a = g = 9.81 m/s
t = 2.0 s
v = 12 m/s
Solution
height of cliff = 44 m
81. 204 m, 59.9 west of south
Given
d = 125 m
d = 105 m
 = 35.0 west of south
 = 90.0 west of south
Solution
d = 204 m, 59.9 west of south
82. 9.75 cm/s
Given
v = 1.00 cm/s
x = 17.5 cm
t = 2.00 s
Solution
83. 12.0 m/s
Given
a = g = 9.81 m/s
x = 8.00 m
t = 3.00 s
Solution
84. 15 m/s
Given
a = g = 9.81 m/s
v = 0.0 m/s
t = 1.5 s
Solution
speed = 15 m/s
85. 48 N
Given
F = 8.0  10 N
 = 53
Solution