Chapter 4
Review
Chapter 4 Review
2) While an object is in projectile motion (with upward being
positive) with no air resistance
A) the horizontal component of its velocity remains constant and
the horizontal component of its acceleration is equal to -g.
B) the horizontal component of its velocity remains constant and
the vertical component of its acceleration is equal to –g
C) the horizontal component of its velocity remains constant and
the vertical component of its acceleration is equal to zero.
D) the vertical component of both its velocity and its
acceleration remain constant.
E) the vertical component of its velocity remains constant and
the vertical component of its acceleration is equal to -g.
Chapter 4 Review
2) While an object is in projectile motion (with upward being
positive) with no air resistance
A) the horizontal component of its velocity remains constant and
the horizontal component of its acceleration is equal to -g.
B) the horizontal component of its velocity remains constant and
the vertical component of its acceleration is equal to –g
C) the horizontal component of its velocity remains constant and
the vertical component of its acceleration is equal to zero.
D) the vertical component of both its velocity and its
acceleration remain constant.
E) the vertical component of its velocity remains constant and
the vertical component of its acceleration is equal to -g.
Ans: B
Chapter 4 Review
3) For general projectile motion, when the
projectile is at the highest point of its trajectory
A) its acceleration is zero.
B) its velocity is perpendicular to the acceleration.
C) its velocity and acceleration are both zero.
D) the horizontal component of its velocity is zero.
E) the horizontal and vertical components of its velocity are zero.
Chapter 4 Review
3) For general projectile motion, when the
projectile is at the highest point of its trajectory
A) its acceleration is zero.
B) its velocity is perpendicular to the acceleration.
C) its velocity and acceleration are both zero.
D) the horizontal component of its velocity is zero.
E) the horizontal and vertical components of its velocity are zero.
Ans: B
Chapter 4 Review
4) Alice and Tom dive from an overhang into the lake below.
Tom simply drops straight down from the edge, but Alice takes
a running start and jumps with an initial horizontal velocity of
25 m/s. Neither person experiences any significant air
resistance. Just as they reach the lake below
A) the speed of Alice is larger than that of Tom.
B) the splashdown speed of Alice is larger than that of Tom.
C) they will both have the same speed.
D) the speed of Tom will always be 9.8 m/s larger than that of
Alice.
E) the speed of Alice will always be 25 m/s larger than that of
Tom.
Chapter 4 Review
4) Alice and Tom dive from an overhang into the lake below.
Tom simply drops straight down from the edge, but Alice takes
a running start and jumps with an initial horizontal velocity of
25 m/s. Neither person experiences any significant air
resistance. Just as they reach the lake below
A) the speed of Alice is larger than that of Tom.
B) the splashdown speed of Alice is larger than that of Tom.
C) they will both have the same speed.
D) the speed of Tom will always be 9.8 m/s larger than that of
Alice.
E) the speed of Alice will always be 25 m/s larger than that of
Tom.
ANS:A
Chapter 4 Review
5) Alice and Tom dive from an overhang into the lake below.
Tom simply drops straight down from the edge, but Alice takes
a running start and jumps with an initial horizontal velocity of
25 m/s. Neither person experiences any significant air
resistance. Compare the time it takes each of them to reach the
lake below.
A) Alice reaches the surface of the lake first.
B) Tom reaches the surface of the lake first.
C) Alice and Tom will reach the surface of the lake at the same
time.
Chapter 4 Review
5) Alice and Tom dive from an overhang into the lake below.
Tom simply drops straight down from the edge, but Alice takes
a running start and jumps with an initial horizontal velocity of
25 m/s. Neither person experiences any significant air
resistance. Compare the time it takes each of them to reach the
lake below.
A) Alice reaches the surface of the lake first.
B) Tom reaches the surface of the lake first.
C) Alice and Tom will reach the surface of the lake at the same
time.
ANS: C
Chapter 4 Review
7) A monkey is sitting at the top of a tree 20 m above ground
level. A person standing on the ground wants to feed the
monkey. He uses a bow and arrow to launch the food to the
monkey. If the person knows that the monkey is going to drop
from the tree at the same instant that the person launches the
food, how should the person aim the arrow containing the
food? Air resistance is small enough to be ignored.
A) He should aim it at the monkey.
B) He should aim it below the monkey.
C) He should aim it above the monkey.
Chapter 4 Review
7) A monkey is sitting at the top of a tree 20 m above ground
level. A person standing on the ground wants to feed the
monkey. He uses a bow and arrow to launch the food to the
monkey. If the person knows that the monkey is going to drop
from the tree at the same instant that the person launches the
food, how should the person aim the arrow containing the
food? Air resistance is small enough to be ignored.
A) He should aim it at the monkey.
B) He should aim it below the monkey.
C) He should aim it above the monkey.
ANS: A
Chapter 4 Review
9) For an object in uniform circular motion, its velocity and
acceleration vectors are always
perpendicular to each other at every point in the path.
A) True
B) False
Chapter 4 Review
9) For an object in uniform circular motion, its velocity and
acceleration vectors are always
perpendicular to each other at every point in the path.
A) True
B) False
ANS: A
Chapter 4 Review
10) If an object travels at a constant speed in a circular
path, the acceleration of the object is
A) larger in magnitude the smaller the radius of the circle.
B) in the same direction as the velocity of the object.
C) smaller in magnitude the smaller the radius of the circle.
D) in the opposite direction of the velocity of the object.
E) zero.
Chapter 4 Review
10) If an object travels at a constant speed in a circular
path, the acceleration of the object is
A) larger in magnitude the smaller the radius of the circle.
B) in the same direction as the velocity of the object.
C) smaller in magnitude the smaller the radius of the circle.
D) in the opposite direction of the velocity of the object.
E) zero.
Answer: A
Chapter 4 Review
6) A hockey puck slides off the edge of a table at point A with
an initial velocity of 20.0 m/s and experiences no air resistance.
The height of the tabletop above the ground is 2.00 m.
(a) What is the speed (not the velocity) of the puck just before it
touches the ground?
(b) What is the distance between point A and the point where
the puck hits the ground?
Chapter 4 Review
6) A hockey puck slides off the edge of a table at point A with
an initial velocity of 20.0 m/s and experiences no air resistance.
The height of the tabletop above the ground is 2.00 m.
(a) What is the speed (not the velocity) of the puck just before it
touches the ground?
ANS: 21.0 m/a
(b) What is the distance between point A and the point where
the puck hits the ground?
ANS: 12.9 m
Chapter 4 Review
7) A hockey puck slides off the edge of a table with an initial
velocity of 28.0 m/s. and experiences no air resistance. The
height of the tabletop above the ground is 2.00 m. What is
the angle below the horizontal of the velocity of the puck just
before it hits the ground?
Chapter 4 Review
7) A hockey puck slides off the edge of a table with an initial
velocity of 28.0 m/s. and experiences no air resistance. The
height of the tabletop above the ground is 2.00 m. What is
the angle below the horizontal of the velocity of the puck just
before it hits the ground?
ANS: 12.6 °
Chapter 4 Review
8) A boy throws a rock with an initial velocity of 2.15 m/s at
30.0° above the horizontal. If air resistance is negligible, how
long does it take for the rock to reach the maximum height of
its trajectory?
Chapter 4 Review
8) A boy throws a rock with an initial velocity of 2.15 m/s at
30.0° above the horizontal. If air resistance is negligible, how
long does it take for the rock to reach the maximum height of
its trajectory?
ANS: 0.110 s
Chapter 4 Review
10) A catapult is tested by Roman legionnaires. They tabulate
the results in a papyrus and 2000 years later the archaeological
team reads (distances translated into modern units):
Range = 0.20 km; angle of launch = π/4; landing height = launch
height. What is the initial velocity of launch of the boulders if
air resistance is negligible?
Chapter 4 Review
10) A catapult is tested by Roman legionnaires. They tabulate
the results in a papyrus and 2000 years later the archaeological
team reads (distances translated into modern units):
Range = 0.20 km; angle of launch = π/4; landing height = launch
height. What is the initial velocity of launch of the boulders if
air resistance is negligible?
ANS 44.0 m/s
Chapter 4 Review
19) A hiker throws a stone from the upper edge of a vertical cliff. The stone's initial
velocity is 25.0 m/s directed at 40.0° with the face of the cliff, as shown in the figure.
The stone hits the ground 3.75 s after being thrown and feels no appreciable air
resistance as it falls.
(a) What is the height of the cliff?
(b) How far from the foot of the cliff does the stone land?
(c) How fast is the stone moving just before it hits the ground?
Chapter 4 Review
19) A hiker throws a stone from the upper edge of a vertical cliff. The stone's initial
velocity is 25.0 m/s directed at 40.0° with the face of the cliff, as shown in the figure.
The stone hits the ground 3.75 s after being thrown and feels no appreciable air
resistance as it falls.
(a) What is the height of the cliff?
(b) How far from the foot of the cliff does the stone land?
(c) How fast is the stone moving just before it hits the ground?
Answer: (a) 141 m (b) 60.3 m (c) 58.2 m/s
Chapter 4 Review
24) A plane has an eastward heading at a speed of 156 m/s
(relative to the air). A 20.0 m/s wind is blowing southward while
the plane is flying. The velocity of the plane relative to the
ground is:
Chapter 4 Review
24) A plane has an eastward heading at a speed of 156 m/s
(relative to the air). A 20.0 m/s wind is blowing southward while
the plane is flying. The velocity of the plane relative to the
ground is:
Ans: 157 m/s at an angle 7.31° south of east.
Chapter 4 Review
32) An electrical motor spins at a constant 2857.0 rev/min. If
the armature radius is 2.685 cm, what is the acceleration of the
outer edge of the armature?
Chapter 4 Review
32) An electrical motor spins at a constant 2857.0 rev/min. If
the armature radius is 2.685 cm, what is the acceleration of the
outer edge of the armature?
ANS: 2403 m/s2
Chapter 4 Review
During a rainstorm, raindrops are observed to be striking the
ground at an angle of 35 degrees with the vertical. The wind
speed is 4.5 m/s. Assuming that the horizontal velocity
component of the raindrops is the same as the speed of the air,
what is the vertical velocity component of the raindrops? What
is their speed?
Chapter 4 Review
During a rainstorm, raindrops are observed to be striking the
ground at an angle of 35 degrees with the vertical. The wind
speed is 4.5 m/s. Assuming that the horizontal velocity
component of the raindrops is the same as the speed of the air,
what is the vertical velocity component of the raindrops? What
is their speed?
Ans: 6.43 m/s down
7.84 m/s
5.52
Chapter 4 Review
A rowboat is pointing perpendicular to the bank of a river. The
rower can propel the boat with a speed of 3.0 m/s with respect
to the water. The river has a current of 4.0 m/s. If the river is
100. m wide, determine how far downstream of the launch point
the rowboat is when it reaches the opposite bank.
Chapter 4 Review
A rowboat is pointing perpendicular to the bank of a river. The
rower can propel the boat with a speed of 3.0 m/s with respect
to the water. The river has a current of 4.0 m/s. If the river is
100. m wide, determine how far downstream of the launch point
the rowboat is when it reaches the opposite bank.
ANS: 130 m
5.53