Section 3 Free Fall: Practice Problems

41.

A construction worker accidentally drops a brick from a high scaffold.

a.

Whatisthevelocityofthebrickafter4.0s?

b.

How far does the brick fall during this time?

SOLUTION:

a. Let upward be the positive direction.

b.

The brick falls 78 m.

ANSWER:

a. Let upward be the positive direction.

v

f

= 39 m/s downward

b. x =

–78m

Thebrickfalls78m.

44.Atennisballisthrownstraightupwithaninitialspeedof22.5m/s.Itiscaughtatthesamedistanceabovethe

ground.

a.

How high does the ball rise?

b.

How long does the ball remain in the air? Hint: The time it takes the ball to rise equals the time it takes to fall.

SOLUTION:

a.

b.

ANSWER:

a. x = 26 m

b. t = 4.6 s

45.

You decide to flip a coin to determine whether to do your physics or English homework first. The coin is flipped

straight up.

a.

What is the velocity of the coin at the top of its trajectory?

b.

Ifthecoinreachesahighpointof0.25mabovewhereyoureleasedit,whatwasitsinitialspeed?

c.

If you catch it at the same height as you released it, how much time did it spend in the air?

SOLUTION:

a. v

top

= 0 m/s; a

top

= 9.8 m/s downward

b.

c.

ANSWER:

a. v

top

= 0 m/s; a

top

= 9.8 m/s downward

b. v

i

= 2.2 m/s

c. t = 0.45 s

Section 3 Free Fall: Review

47.

MAIN IDEA

Suppose you hold a book in one hand and a flat sheet of paper in another hand. You drop them both,

and they fall to the ground. Explain why the falling book is a good example of free fall, but the paper is not.

SOLUTION:

Free fall is the motion of an object when gravity is the only significant force on it. The paper is

significantly affected by the air, but the book is not.

ANSWER:

Free fall is the motion of an object when gravity is the only significant force on it. The paper is

significantly affected by the air, but the book is not.

49.

Free-Fall Ride

Suppose a free-fall ride at an amusement park starts at rest and is in free fall. What is the velocity

oftherideafter2.3s?Howfardopeopleontheridefallduringthe2.3

-s time period?

SOLUTION:

Let upward be the positive direction.

ANSWER:

Let upward be the positive direction.

v

f

= 23 m/s downward

x

f

=

−

26 m

The people fall 26 m during the 2.3-s time period.

51.

Velocity and Acceleration

Suppose you throw a ball straight up into the air. Describe the changes in the velocity of

the ball. Describe the changes in the acceleration of the ball.

SOLUTION:

Velocity is reduced at a constant rate as the ball travels upward. At its highest point, velocity is zero. As

the ball begins to drop, the velocity begins to increase in the negative direction. When it reaches the

height from which it was initially released, the ball has the same speed it had upon release. The

acceleration is constant throughout the ball

’sflight.

ANSWER:

Velocity is reduced at a constant rate as the ball travels upward. At its highest point, velocity is zero. As

the ball begins to drop, the velocity begins to increase in the negative direction. When it reaches the

height from which it was initially released, the ball has the same speed it had upon release. The

acceleration is constant throughout the ball

’sflight.

Chapter Assessment

Section 3 Free Fall: Mastering Problems

72.Astonethatstartsatrestisinfreefallfor8.0s.(Level1)

a.

Calculate the stone

’svelocityafter8.0s.

b.

What is the stone

’

s displacement during this time?

SOLUTION:

a. v

f

= v

i

+ at

f

where a =

−

9.8 m/s

2

= 0.0 m/s + (

−

9.8 m/s

2

)(8.0 s)

=

−

78 m/s

= 78 m/s downward

b. Choose the coordinate system to have the origin where the stone is at rest and positive to be upward.

=3.1×10

2

m downward

ANSWER:

a. 78 m/s downward

b. 310 m downward

74.Youthrowaballdownwardfromawindowataspeedof2.0m/s.Howfastwillitbemovingwhenithitsthe

sidewalk2.5mbelow?(Level2)

SOLUTION:

Choose a coordinate system with the positive direction downward and the origin at the point where the

ball leaves your hand.

ANSWER:

Choose a coordinate system with the positive direction downward and the origin at the point where the

ball leaves your hand.

76.

Beanbag

Youthrowabeanbagintheairandcatchit2.2slateratthesameplaceatwhichyouthrewit.(Level3)

a.

How high did it go?

b.

What was its initial velocity?

SOLUTION:

a. Choose a coordinate system with the upward direction positive. The time to reach the maximum height

is half of the time in the air.

b.

v

i

= 11 m/s upward

ANSWER:

a. Choose a coordinate system with the upward direction positive. The time to reach the maximum height

ishalfofthetimeintheair.

v

i

=10.78m/s

x

f

= 5.9 m

b.

v

i

= 11 m/s upward

Chapter Assessment: Mixed Review

88.

Bicycle

Abicycleacceleratesfrom0.0m/sto4.0m/sin4.0s.Whatdistancedoesittravel?(Level1)

SOLUTION:

ANSWER:

8.0 m

89.AweatherballoonisfloatingataconstantheightaboveEarthwhenitreleasesapackofinstruments.(Level1)

a.

If the pack hits the ground with a downward velocity of

−73.5m/s,howfardidthepackfall?

b.

Calculatethedistancetheballhasrolledattheendof2.2s.

SOLUTION:

a.

b.

ANSWER:

a. x

f

=2.8×10

2

m downward

b. t

f

= 7.5 s

eSolutionsManual-PoweredbyCogneroPage1

Chapter 3 Practice Problems, Review, and Assessment

Section 3 Free Fall: Practice Problems

41.

A construction worker accidentally drops a brick from a high scaffold.

a.

Whatisthevelocityofthebrickafter4.0s?

b.

How far does the brick fall during this time?

SOLUTION:

a. Let upward be the positive direction.

b.

The brick falls 78 m.

ANSWER:

a. Let upward be the positive direction.

v

f

= 39 m/s downward

b. x =

–78m

Thebrickfalls78m.

44.Atennisballisthrownstraightupwithaninitialspeedof22.5m/s.Itiscaughtatthesamedistanceabovethe

ground.

a.

How high does the ball rise?

b.

How long does the ball remain in the air? Hint: The time it takes the ball to rise equals the time it takes to fall.

SOLUTION:

a.

b.

ANSWER:

a. x = 26 m

b. t = 4.6 s

45.

You decide to flip a coin to determine whether to do your physics or English homework first. The coin is flipped

straight up.

a.

What is the velocity of the coin at the top of its trajectory?

b.

Ifthecoinreachesahighpointof0.25mabovewhereyoureleasedit,whatwasitsinitialspeed?

c.

If you catch it at the same height as you released it, how much time did it spend in the air?

SOLUTION:

a. v

top

= 0 m/s; a

top

= 9.8 m/s downward

b.

c.

ANSWER:

a. v

top

= 0 m/s; a

top

= 9.8 m/s downward

b. v

i

= 2.2 m/s

c. t = 0.45 s

Section 3 Free Fall: Review

47.

MAIN IDEA

Suppose you hold a book in one hand and a flat sheet of paper in another hand. You drop them both,

and they fall to the ground. Explain why the falling book is a good example of free fall, but the paper is not.

SOLUTION:

Free fall is the motion of an object when gravity is the only significant force on it. The paper is

significantly affected by the air, but the book is not.

ANSWER:

Free fall is the motion of an object when gravity is the only significant force on it. The paper is

significantly affected by the air, but the book is not.

49.

Free-Fall Ride

Suppose a free-fall ride at an amusement park starts at rest and is in free fall. What is the velocity

oftherideafter2.3s?Howfardopeopleontheridefallduringthe2.3

-s time period?

SOLUTION:

Let upward be the positive direction.

ANSWER:

Let upward be the positive direction.

v

f

= 23 m/s downward

x

f

=

−

26 m

The people fall 26 m during the 2.3-s time period.

51.

Velocity and Acceleration

Suppose you throw a ball straight up into the air. Describe the changes in the velocity of

the ball. Describe the changes in the acceleration of the ball.

SOLUTION:

Velocity is reduced at a constant rate as the ball travels upward. At its highest point, velocity is zero. As

the ball begins to drop, the velocity begins to increase in the negative direction. When it reaches the

height from which it was initially released, the ball has the same speed it had upon release. The

acceleration is constant throughout the ball

’sflight.

ANSWER:

height from which it was initially released, the ball has the same speed it had upon release. The

acceleration is constant throughout the ball

’sflight.

Chapter Assessment

Section 3 Free Fall: Mastering Problems

72.Astonethatstartsatrestisinfreefallfor8.0s.(Level1)

a.

Calculate the stone

’svelocityafter8.0s.

b.

What is the stone

’

s displacement during this time?

SOLUTION:

a. v

f

= v

i

+ at

f

where a =

−

9.8 m/s

2

= 0.0 m/s + (

−

9.8 m/s

2

)(8.0 s)

=

−

78 m/s

= 78 m/s downward

b. Choose the coordinate system to have the origin where the stone is at rest and positive to be upward.

=3.1×10

2

m downward

ANSWER:

a. 78 m/s downward

b. 310 m downward

74.Youthrowaballdownwardfromawindowataspeedof2.0m/s.Howfastwillitbemovingwhenithitsthe

sidewalk2.5mbelow?(Level2)

SOLUTION:

Choose a coordinate system with the positive direction downward and the origin at the point where the

ball leaves your hand.

ANSWER:

ball leaves your hand.

76.

Beanbag

Youthrowabeanbagintheairandcatchit2.2slateratthesameplaceatwhichyouthrewit.(Level3)

a.

How high did it go?

b.

What was its initial velocity?

SOLUTION:

a. Choose a coordinate system with the upward direction positive. The time to reach the maximum height

is half of the time in the air.

b.

v

i

= 11 m/s upward

ANSWER:

ishalfofthetimeintheair.

v

i

=10.78m/s

x

f

= 5.9 m

b.

v

i

= 11 m/s upward

Chapter Assessment: Mixed Review

88.

Bicycle

Abicycleacceleratesfrom0.0m/sto4.0m/sin4.0s.Whatdistancedoesittravel?(Level1)

SOLUTION:

ANSWER:

8.0 m

89.AweatherballoonisfloatingataconstantheightaboveEarthwhenitreleasesapackofinstruments.(Level1)

a.

If the pack hits the ground with a downward velocity of

−73.5m/s,howfardidthepackfall?

b.

Calculatethedistancetheballhasrolledattheendof2.2s.

SOLUTION:

a.

b.

ANSWER:

a. x

f

=2.8×10

2

m downward

b. t

f

= 7.5 s

eSolutionsManual-PoweredbyCogneroPage2

Chapter 3 Practice Problems, Review, and Assessment

Section 3 Free Fall: Practice Problems

41.

A construction worker accidentally drops a brick from a high scaffold.

a.

Whatisthevelocityofthebrickafter4.0s?

b.

How far does the brick fall during this time?

SOLUTION:

a. Let upward be the positive direction.

b.

The brick falls 78 m.

ANSWER:

a. Let upward be the positive direction.

v

f

= 39 m/s downward

b. x =

–78m

Thebrickfalls78m.

44.Atennisballisthrownstraightupwithaninitialspeedof22.5m/s.Itiscaughtatthesamedistanceabovethe

ground.

a.

How high does the ball rise?

b.

How long does the ball remain in the air? Hint: The time it takes the ball to rise equals the time it takes to fall.

SOLUTION:

a.

b.

ANSWER:

a. x = 26 m

b. t = 4.6 s

45.

You decide to flip a coin to determine whether to do your physics or English homework first. The coin is flipped

straight up.

a.

What is the velocity of the coin at the top of its trajectory?

b.

Ifthecoinreachesahighpointof0.25mabovewhereyoureleasedit,whatwasitsinitialspeed?

c.

If you catch it at the same height as you released it, how much time did it spend in the air?

SOLUTION:

a. v

top

= 0 m/s; a

top

= 9.8 m/s downward

b.

c.

ANSWER:

a. v

top

= 0 m/s; a

top

= 9.8 m/s downward

b. v

i

= 2.2 m/s

c. t = 0.45 s

Section 3 Free Fall: Review

47.

MAIN IDEA

Suppose you hold a book in one hand and a flat sheet of paper in another hand. You drop them both,

and they fall to the ground. Explain why the falling book is a good example of free fall, but the paper is not.

SOLUTION:

Free fall is the motion of an object when gravity is the only significant force on it. The paper is

significantly affected by the air, but the book is not.

ANSWER:

Free fall is the motion of an object when gravity is the only significant force on it. The paper is

significantly affected by the air, but the book is not.

49.

Free-Fall Ride

Suppose a free-fall ride at an amusement park starts at rest and is in free fall. What is the velocity

oftherideafter2.3s?Howfardopeopleontheridefallduringthe2.3

-s time period?

SOLUTION:

Let upward be the positive direction.

ANSWER:

Let upward be the positive direction.

v

f

= 23 m/s downward

x

f

=

−

26 m

The people fall 26 m during the 2.3-s time period.

51.

Velocity and Acceleration

Suppose you throw a ball straight up into the air. Describe the changes in the velocity of

the ball. Describe the changes in the acceleration of the ball.

SOLUTION:

height from which it was initially released, the ball has the same speed it had upon release. The

acceleration is constant throughout the ball

’sflight.

ANSWER:

height from which it was initially released, the ball has the same speed it had upon release. The

acceleration is constant throughout the ball

’sflight.

Chapter Assessment

Section 3 Free Fall: Mastering Problems

72.Astonethatstartsatrestisinfreefallfor8.0s.(Level1)

a.

Calculate the stone

’svelocityafter8.0s.

b.

What is the stone

’

s displacement during this time?

SOLUTION:

a. v

f

= v

i

+ at

f

where a =

−

9.8 m/s

2

= 0.0 m/s + (

−

9.8 m/s

2

)(8.0 s)

=

−

78 m/s

= 78 m/s downward

b. Choose the coordinate system to have the origin where the stone is at rest and positive to be upward.

=3.1×10

2

m downward

ANSWER:

a. 78 m/s downward

b. 310 m downward

74.Youthrowaballdownwardfromawindowataspeedof2.0m/s.Howfastwillitbemovingwhenithitsthe

sidewalk2.5mbelow?(Level2)

SOLUTION:

ball leaves your hand.

ANSWER:

ball leaves your hand.

76.

Beanbag

Youthrowabeanbagintheairandcatchit2.2slateratthesameplaceatwhichyouthrewit.(Level3)

a.

How high did it go?

b.

What was its initial velocity?

SOLUTION:

is half of the time in the air.

b.

v

i

= 11 m/s upward

ANSWER:

ishalfofthetimeintheair.

v

i

=10.78m/s

x

f

= 5.9 m

b.

v

i

= 11 m/s upward

Chapter Assessment: Mixed Review

88.

Bicycle

Abicycleacceleratesfrom0.0m/sto4.0m/sin4.0s.Whatdistancedoesittravel?(Level1)

SOLUTION:

ANSWER:

8.0 m

89.AweatherballoonisfloatingataconstantheightaboveEarthwhenitreleasesapackofinstruments.(Level1)

a.

If the pack hits the ground with a downward velocity of

−73.5m/s,howfardidthepackfall?

b.

Calculatethedistancetheballhasrolledattheendof2.2s.

SOLUTION:

a.

b.

ANSWER:

a. x

f

=2.8×10

2

m downward

b. t

f

= 7.5 s

eSolutionsManual-PoweredbyCogneroPage3

Chapter 3 Practice Problems, Review, and Assessment

Section 3 Free Fall: Practice Problems

41.

A construction worker accidentally drops a brick from a high scaffold.

a.

Whatisthevelocityofthebrickafter4.0s?

b.

How far does the brick fall during this time?

SOLUTION:

a. Let upward be the positive direction.

b.

The brick falls 78 m.

ANSWER:

a. Let upward be the positive direction.

v

f

= 39 m/s downward

b. x =

–78m

Thebrickfalls78m.

ground.

a.

How high does the ball rise?

b.

SOLUTION:

a.

b.

ANSWER:

a. x = 26 m

b. t = 4.6 s

45.

straight up.

a.

What is the velocity of the coin at the top of its trajectory?

b.

Ifthecoinreachesahighpointof0.25mabovewhereyoureleasedit,whatwasitsinitialspeed?

c.

If you catch it at the same height as you released it, how much time did it spend in the air?

SOLUTION:

a. v

top

= 0 m/s; a

top

= 9.8 m/s downward

b.

c.

ANSWER:

a. v

top

= 0 m/s; a

top

= 9.8 m/s downward

b. v

i

= 2.2 m/s

c. t = 0.45 s

Section 3 Free Fall: Review

47.

MAIN IDEA

Suppose you hold a book in one hand and a flat sheet of paper in another hand. You drop them both,

SOLUTION:

Free fall is the motion of an object when gravity is the only significant force on it. The paper is

significantly affected by the air, but the book is not.

ANSWER:

Free fall is the motion of an object when gravity is the only significant force on it. The paper is

significantly affected by the air, but the book is not.

49.

Free-Fall Ride

oftherideafter2.3s?Howfardopeopleontheridefallduringthe2.3

-s time period?

SOLUTION:

Let upward be the positive direction.

ANSWER:

Let upward be the positive direction.

v

f

= 23 m/s downward

x

f

=

−

26 m

The people fall 26 m during the 2.3-s time period.

51.

Velocity and Acceleration

Suppose you throw a ball straight up into the air. Describe the changes in the velocity of

the ball. Describe the changes in the acceleration of the ball.

SOLUTION:

height from which it was initially released, the ball has the same speed it had upon release. The

acceleration is constant throughout the ball

’sflight.

ANSWER:

height from which it was initially released, the ball has the same speed it had upon release. The

acceleration is constant throughout the ball

’sflight.

Chapter Assessment

Section 3 Free Fall: Mastering Problems

72.Astonethatstartsatrestisinfreefallfor8.0s.(Level1)

a.

Calculate the stone

’svelocityafter8.0s.

b.

What is the stone

’

s displacement during this time?

SOLUTION:

a. v

f

= v

i

+ at

f

where a =

−

9.8 m/s

2

= 0.0 m/s + (

−

9.8 m/s

2

)(8.0 s)

=

−

78 m/s

= 78 m/s downward

=3.1×10

2

m downward

ANSWER:

a. 78 m/s downward

b. 310 m downward

sidewalk2.5mbelow?(Level2)

SOLUTION:

ball leaves your hand.

ANSWER:

ball leaves your hand.

76.

Beanbag

a.

How high did it go?

b.

What was its initial velocity?

SOLUTION:

is half of the time in the air.

b.

v

i

= 11 m/s upward

ANSWER:

ishalfofthetimeintheair.

v

i

=10.78m/s

x

f

= 5.9 m

b.

v

i

= 11 m/s upward

Chapter Assessment: Mixed Review

88.

Bicycle

Abicycleacceleratesfrom0.0m/sto4.0m/sin4.0s.Whatdistancedoesittravel?(Level1)

SOLUTION:

ANSWER:

8.0 m

a.

If the pack hits the ground with a downward velocity of

−73.5m/s,howfardidthepackfall?

b.

Calculatethedistancetheballhasrolledattheendof2.2s.

SOLUTION:

a.

b.

ANSWER:

a. x

f

=2.8×10

2

m downward

b. t

f

= 7.5 s

eSolutionsManual-PoweredbyCogneroPage4

Chapter 3 Practice Problems, Review, and Assessment

Section 3 Free Fall: Practice Problems

41.

A construction worker accidentally drops a brick from a high scaffold.

a.

Whatisthevelocityofthebrickafter4.0s?

b.

How far does the brick fall during this time?

SOLUTION:

a. Let upward be the positive direction.

b.

The brick falls 78 m.

ANSWER:

a. Let upward be the positive direction.

v

f

= 39 m/s downward

b. x =

–78m

Thebrickfalls78m.

ground.

a.

How high does the ball rise?

b.

SOLUTION:

a.

b.

ANSWER:

a. x = 26 m

b. t = 4.6 s

45.

straight up.

a.

What is the velocity of the coin at the top of its trajectory?

b.

Ifthecoinreachesahighpointof0.25mabovewhereyoureleasedit,whatwasitsinitialspeed?

c.

If you catch it at the same height as you released it, how much time did it spend in the air?

SOLUTION:

a. v

top

= 0 m/s; a

top

= 9.8 m/s downward

b.

c.

ANSWER:

a. v

top

= 0 m/s; a

top

= 9.8 m/s downward

b. v

i

= 2.2 m/s

c. t = 0.45 s

Section 3 Free Fall: Review

47.

MAIN IDEA

Suppose you hold a book in one hand and a flat sheet of paper in another hand. You drop them both,

SOLUTION:

Free fall is the motion of an object when gravity is the only significant force on it. The paper is

significantly affected by the air, but the book is not.

ANSWER:

Free fall is the motion of an object when gravity is the only significant force on it. The paper is

significantly affected by the air, but the book is not.

49.

Free-Fall Ride

oftherideafter2.3s?Howfardopeopleontheridefallduringthe2.3

-s time period?

SOLUTION:

Let upward be the positive direction.

ANSWER:

Let upward be the positive direction.

v

f

= 23 m/s downward

x

f

=

−

26 m

The people fall 26 m during the 2.3-s time period.

51.

Velocity and Acceleration

Suppose you throw a ball straight up into the air. Describe the changes in the velocity of

the ball. Describe the changes in the acceleration of the ball.

SOLUTION:

height from which it was initially released, the ball has the same speed it had upon release. The

acceleration is constant throughout the ball

’sflight.

ANSWER:

height from which it was initially released, the ball has the same speed it had upon release. The

acceleration is constant throughout the ball

’sflight.

Chapter Assessment

Section 3 Free Fall: Mastering Problems

72.Astonethatstartsatrestisinfreefallfor8.0s.(Level1)

a.

Calculate the stone

’svelocityafter8.0s.

b.

What is the stone

’

s displacement during this time?

SOLUTION:

a. v

f

= v

i

+ at

f

where a =

−

9.8 m/s

2

= 0.0 m/s + (

−

9.8 m/s

2

)(8.0 s)

=

−

78 m/s

= 78 m/s downward

=3.1×10

2

m downward

ANSWER:

a. 78 m/s downward

b. 310 m downward

sidewalk2.5mbelow?(Level2)

SOLUTION:

ball leaves your hand.

ANSWER:

ball leaves your hand.

76.

Beanbag

a.

How high did it go?

b.

What was its initial velocity?

SOLUTION:

is half of the time in the air.

b.

v

i

= 11 m/s upward

ANSWER:

ishalfofthetimeintheair.

v

i

=10.78m/s

x

f

= 5.9 m

b.

v

i

= 11 m/s upward

Chapter Assessment: Mixed Review

88.

Bicycle

Abicycleacceleratesfrom0.0m/sto4.0m/sin4.0s.Whatdistancedoesittravel?(Level1)

SOLUTION:

ANSWER:

8.0 m

a.

If the pack hits the ground with a downward velocity of

−73.5m/s,howfardidthepackfall?

b.

Calculatethedistancetheballhasrolledattheendof2.2s.

SOLUTION:

a.

b.

ANSWER:

a. x

f

=2.8×10

2

m downward

b. t

f

= 7.5 s

eSolutionsManual-PoweredbyCogneroPage5

Chapter 3 Practice Problems, Review, and Assessment

Section 3 Free Fall: Practice Problems

41.

A construction worker accidentally drops a brick from a high scaffold.

a.

Whatisthevelocityofthebrickafter4.0s?

b.

How far does the brick fall during this time?

SOLUTION:

a. Let upward be the positive direction.

b.

The brick falls 78 m.

ANSWER:

a. Let upward be the positive direction.

v

f

= 39 m/s downward

b. x =

–78m

Thebrickfalls78m.

ground.

a.

How high does the ball rise?

b.

SOLUTION:

a.

b.

ANSWER:

a. x = 26 m

b. t = 4.6 s

45.

straight up.

a.

What is the velocity of the coin at the top of its trajectory?

b.

Ifthecoinreachesahighpointof0.25mabovewhereyoureleasedit,whatwasitsinitialspeed?

c.

If you catch it at the same height as you released it, how much time did it spend in the air?

SOLUTION:

a. v

top

= 0 m/s; a

top

= 9.8 m/s downward

b.

c.

ANSWER:

a. v

top

= 0 m/s; a

top

= 9.8 m/s downward

b. v

i

= 2.2 m/s

c. t = 0.45 s

Section 3 Free Fall: Review

47.

MAIN IDEA

Suppose you hold a book in one hand and a flat sheet of paper in another hand. You drop them both,

SOLUTION:

Free fall is the motion of an object when gravity is the only significant force on it. The paper is

significantly affected by the air, but the book is not.

ANSWER:

Free fall is the motion of an object when gravity is the only significant force on it. The paper is

significantly affected by the air, but the book is not.

49.

Free-Fall Ride

oftherideafter2.3s?Howfardopeopleontheridefallduringthe2.3

-s time period?

SOLUTION:

Let upward be the positive direction.

ANSWER:

Let upward be the positive direction.

v

f

= 23 m/s downward

x

f

=

−

26 m

The people fall 26 m during the 2.3-s time period.

51.

Velocity and Acceleration

Suppose you throw a ball straight up into the air. Describe the changes in the velocity of

the ball. Describe the changes in the acceleration of the ball.

SOLUTION:

height from which it was initially released, the ball has the same speed it had upon release. The

acceleration is constant throughout the ball

’sflight.

ANSWER:

height from which it was initially released, the ball has the same speed it had upon release. The

acceleration is constant throughout the ball

’sflight.

Chapter Assessment

Section 3 Free Fall: Mastering Problems

72.Astonethatstartsatrestisinfreefallfor8.0s.(Level1)

a.

Calculate the stone

’svelocityafter8.0s.

b.

What is the stone

’

s displacement during this time?

SOLUTION:

a. v

f

= v

i

+ at

f

where a =

−

9.8 m/s

2

= 0.0 m/s + (

−

9.8 m/s

2

)(8.0 s)

=

−

78 m/s

= 78 m/s downward

=3.1×10

2

m downward

ANSWER:

a. 78 m/s downward

b. 310 m downward

sidewalk2.5mbelow?(Level2)

SOLUTION:

ball leaves your hand.

ANSWER:

ball leaves your hand.

76.

Beanbag

a.

How high did it go?

b.

What was its initial velocity?

SOLUTION:

is half of the time in the air.

b.

v

i

= 11 m/s upward

ANSWER:

ishalfofthetimeintheair.

v

i

=10.78m/s

x

f

= 5.9 m

b.

v

i

= 11 m/s upward

Chapter Assessment: Mixed Review

88.

Bicycle

Abicycleacceleratesfrom0.0m/sto4.0m/sin4.0s.Whatdistancedoesittravel?(Level1)

SOLUTION:

ANSWER:

8.0 m

a.

If the pack hits the ground with a downward velocity of

−73.5m/s,howfardidthepackfall?

b.

Calculatethedistancetheballhasrolledattheendof2.2s.

SOLUTION:

a.

b.

ANSWER:

a. x

f

=2.8×10

2

m downward

b. t

f

= 7.5 s

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Chapter 3 Practice Problems, Review, and Assessment

Section 3 Free Fall: Practice Problems

41.

A construction worker accidentally drops a brick from a high scaffold.

a.

Whatisthevelocityofthebrickafter4.0s?

b.

How far does the brick fall during this time?

SOLUTION:

a. Let upward be the positive direction.

b.

The brick falls 78 m.

ANSWER:

a. Let upward be the positive direction.

v

f

= 39 m/s downward

b. x =

–78m

Thebrickfalls78m.

ground.

a.

How high does the ball rise?

b.

SOLUTION:

a.

b.

ANSWER:

a. x = 26 m

b. t = 4.6 s

45.

straight up.

a.

What is the velocity of the coin at the top of its trajectory?

b.

Ifthecoinreachesahighpointof0.25mabovewhereyoureleasedit,whatwasitsinitialspeed?

c.

If you catch it at the same height as you released it, how much time did it spend in the air?

SOLUTION:

a. v

top

= 0 m/s; a

top

= 9.8 m/s downward

b.

c.

ANSWER:

a. v

top

= 0 m/s; a

top

= 9.8 m/s downward

b. v

i

= 2.2 m/s

c. t = 0.45 s

Section 3 Free Fall: Review

47.

MAIN IDEA

Suppose you hold a book in one hand and a flat sheet of paper in another hand. You drop them both,

SOLUTION:

Free fall is the motion of an object when gravity is the only significant force on it. The paper is

significantly affected by the air, but the book is not.

ANSWER:

Free fall is the motion of an object when gravity is the only significant force on it. The paper is

significantly affected by the air, but the book is not.

49.

Free-Fall Ride

oftherideafter2.3s?Howfardopeopleontheridefallduringthe2.3

-s time period?

SOLUTION:

Let upward be the positive direction.

ANSWER:

Let upward be the positive direction.

v

f

= 23 m/s downward

x

f

=

−

26 m

The people fall 26 m during the 2.3-s time period.

51.

Velocity and Acceleration

Suppose you throw a ball straight up into the air. Describe the changes in the velocity of

the ball. Describe the changes in the acceleration of the ball.

SOLUTION:

height from which it was initially released, the ball has the same speed it had upon release. The

acceleration is constant throughout the ball

’sflight.

ANSWER:

height from which it was initially released, the ball has the same speed it had upon release. The

acceleration is constant throughout the ball

’sflight.

Chapter Assessment

Section 3 Free Fall: Mastering Problems

72.Astonethatstartsatrestisinfreefallfor8.0s.(Level1)

a.

Calculate the stone

’svelocityafter8.0s.

b.

What is the stone

’

s displacement during this time?

SOLUTION:

a. v

f

= v

i

+ at

f

where a =

−

9.8 m/s

2

= 0.0 m/s + (

−

9.8 m/s

2

)(8.0 s)

=

−

78 m/s

= 78 m/s downward

=3.1×10

2

m downward

ANSWER:

a. 78 m/s downward

b. 310 m downward

sidewalk2.5mbelow?(Level2)

SOLUTION:

ball leaves your hand.

ANSWER:

ball leaves your hand.

76.

Beanbag

a.

How high did it go?

b.

What was its initial velocity?

SOLUTION:

is half of the time in the air.

b.

v

i

= 11 m/s upward

ANSWER:

ishalfofthetimeintheair.

v

i

=10.78m/s

x

f

= 5.9 m

b.

v

i

= 11 m/s upward

Chapter Assessment: Mixed Review

88.

Bicycle

Abicycleacceleratesfrom0.0m/sto4.0m/sin4.0s.Whatdistancedoesittravel?(Level1)

SOLUTION:

ANSWER:

8.0 m

a.

If the pack hits the ground with a downward velocity of

−73.5m/s,howfardidthepackfall?

b.

Calculatethedistancetheballhasrolledattheendof2.2s.

SOLUTION:

a.

b.

ANSWER:

a. x

f

=2.8×10

2

m downward

b. t

f

= 7.5 s

eSolutionsManual-PoweredbyCogneroPage7

Chapter 3 Practice Problems, Review, and Assessment