Concept-Development Practice Page

300

150

100

150

300

600

800

1200

CONCEPTUAL PHYSICS

Chapter 2 Mechanical Equilibrium 3

2-1

Concept-Development

Practice Page

Name Class Date

Static Equilibrium

1. Little Nellie Newton

wishes to be a

gymnast and hangs

from a variety of

positions as shown.

Since she is not

accelerating, the net

force on her is zero.

That is, ∑F = 0. This

means the upward

pull of the rope(s)

equals the down ward

pull of gravity. She

weighs 300 N. Show

the scale reading(s)

for each case.

2. When Burl the painter stands in the exact

middle of his staging, the left scale reads

600 N. Fill in the reading on the right scale.

The total weight of Burl and staging must be

3. Burl stands farther from the left. Fill in the

reading on the right scale.

4. In a silly mood, Burl dangles from the right

end. Fill in the reading on the right scale.

600

350

1000

500

500 500

1000

500

CONCEPTUAL PHYSICS

4 Chapter 2 Mechanical Equilibrium

The Equilibrium Rule: ⌺F = 0

1. Manuel weighs 1000 N and stands in the

middle of a board that weighs 200 N.

The ends of the board rest on bathroom

scales. (We can assume the weight of the

board acts at its center.) Fill in the

correct weight reading on each scale.

2. When Manuel moves to the left as shown, the scale

closest to him reads 850 N. Fill in the weight for the

far scale.

3. A 12-ton truck is one-quarter the way

across a bridge that weighs 20 tons. A

13-ton force supports the right side of

the bridge as shown. How much support

force is on the left side?

4. A 1000-N crate resting on a surface is

connected to a 500-N block through a

frictionless pulley as shown. Friction

between the crate and surface is enough

to keep the system at rest. The arrows

show the forces that act on the crate and

the block. Fill in the magnitude of each

force.

5. If the crate and block in the preceding question move at constant speed, the tension in the rope

(is the same) (increases) (decreases).

The sliding system is then in (static equilibrium) (dynamic equilibrium).

CONCEPTUAL PHYSICS

Chapter 2 Mechanical Equilibrium 5

Name Class Date

Vectors and Equilibrium

1. Nellie Newton dangles

from a vertical rope

in equilibrium:

∑F

= 0.

The tension in the rope

(upward vector) has the same

magnitude as the downward

pull of gravity (downward vector).

2. Nellie is supported by

two vertical ropes.

Draw tension vectors

to scale along the direction

of each rope.

3. This time the vertical ropes

have different lengths. Draw

tension vectors to scale for

each of the two ropes.

4. Nellie is supported by three

vertical ropes that are

equally taut but have

different lengths. Again,

draw tension vectors to scale

for each of the three ropes.

Circle the correct answers.

5. We see that tension in a rope is (dependent on) (independent of) the length of the rope. So the length

of a vector representing rope tension is (dependent on) (independent of) the length of the rope.

2-2

Concept-Development

Practice Page

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≈0

CONCEPTUAL PHYSICS

6 Chapter 2 Mechanical Equilibrium

Net Force

Fill in the magnitudes of net force for each case.

CONCEPTUAL PHYSICS

Chapter 2 Mechanical Equilibrium 7

Name Class Date

Vectors and Equilibrium

The rock hangs at rest from a single string. Only two forces act on it, the upward

tension T of the string, and the downward pull of gravity W. The forces are equal

in magnitude and opposite in direction.

Net force on the rock is (zero) (greater than zero).

Here the rock is suspended by 2 strings. Tension in each string acts in a

direction along the string. We’ll show tension of the left string by vector A,

and tension of the right string by vector B. The resultant of A and B is found by

the parallelogram rule, and is shown by the dashed vector. Note it has the same

magnitude as W, so the net force on the rock is

(zero) (greater than zero).

Consider strings at unequal angles. The resultant A+B is still equal

and opposite to W, and is shown by the dashed vector. Construct the

appropriate parallelogram to produce this resultant. Show the rela-

tive magnitudes of A and B.

Tension in A is (less than) (equal to) (greater than) tension in B.

Repeat the procedure for the arrangement below.

Here tension is greater in .

Construct vectors A and B for the cases below. First draw a vector W, then the parallelogram that has

equal and opposite vector A + B as the diagonal. Then ﬁ nd approximate magnitudes of A and B.

CONCEPTUAL PHYSICS

Chapter 3 Newton’s First Law of Motion—Inertia 9

3-1

Concept-Development

Practice Page

Name Class Date

Mass and Weight

Learning physics is learning the connections among concepts in nature, and

also learning to distinguish between closely related concepts. Velocity and

acceleration, which are treated in the next chapter, are often confused. Similarly

in this chapter, we ﬁ nd that mass and weight are often confused. They aren’t the

same! Please review the distinction between mass and weight in your textbook. To

reinforce your understanding of this distinction, circle the correct answers below.

Comparing the concepts of mass and weight, one is basic—fundamental—

depending only on the internal makeup of an object and the number and kind of atoms that compose

it. The concept that is fundamental is (mass) (weight).

The concept that additionally depends on location in a gravitational ﬁ eld is (mass) (weight).

(Mass) (Weight) is a measure of the amount of matter in an object and only depends on

the number and kind of atoms that compose it.

It can correctly be said that (mass) (weight) is a measure of “laziness” of an object.

(Mass) (Weight) is related to the gravitational force acting on the object.

(Mass) (Weight) depends on an object’s location, whereas (mass) (weight) does not.

In other words, a stone would have the same (mass) (weight) whether it is on the surface of Earth or on

the surface of the moon. However, its (mass) (weight) depends on its location.

On the moon’s surface, where gravity is only about one sixth of Earth gravity (mass) (weight)

(both the mass and the weight) of the stone would be the same as on Earth.

While mass and weight are not the same, they are (directly proportional) (inversely proportional)

to each other. In the same location, twice the mass has (twice) (half) the weight.

The International System of Units (SI) unit of mass is the (kilogram) (newton), and the SI unit of

force is the (kilogram) (newton).

In the United States, it is common to measure the mass of something by measuring its gravitational pull

to Earth, its weight. The common unit of weight in the U.S. is the (pound) (kilogram) (newton).

450 N

99 lb

45.0 kg

1125 N

* Any value for kg as long as the same value is multiplied by 10 for N.

0.1 kg

10 N

600 N

CONCEPTUAL PHYSICS

10 Chapter 3 Newton’s First Law of Motion—Inertia

Converting Mass to Weight

Objects with mass also have weight (although they can be weightless under special conditions). If you

know the mass of something in kilograms and want its weight in newtons, at Earth’s surface, you can

take advantage of the formula that relates weight and mass.

Weight = mass × acceleration due to gravity

W = mg

This is in accord with Newton’s second law, written as

F = ma.

When the force of gravity is the only

force, the acceleration of any object of mass

will be

the acceleration of free fall. Importantly,

acts

as a proportionality constant, 10 N/kg, which is equivalent to 10 m/s

Sample Question:

How much does a 1-kg bag of nails weigh on Earth?

W = mg = (1 kg)(10 m/s

) = 10 m/s

= 10 N,

or simply, W = mg = (1 kg)(10 N/kg) = 10 N.

Answer the following questions.

Felicia the ballet dancer has a mass of 45.0 kg.

1. What is Felicia’s weight in newtons at Earth’s surface?

2. Given that 1 kilogram of mass corresponds to 2.2 pounds at

Earth’s surface, what is Felicia’s weight in pounds on Earth?

3. What would be Felicia’s mass on the surface of Jupiter?

4. What would be Felicia’s weight on Jupiter’s surface,

where the acceleration due to gravity is 25.0 m/s

Different masses are hung on a spring scale calibrated in newtons.

The force exerted by gravity on 1 kg = 10 N.

5. The force exerted by gravity on 5 kg = N.

6. The force exerted by gravity on kg = 100 N.

Make up your own mass and show the corresponding weight:

The force exerted by gravity on kg = N.

By whatever means (spring scales,

measuring balances, etc.), ﬁ nd the

mass of your physics book. Then

complete the table.

A body in motion tends to remain in motion as long as no net force is exerted on the body in

the direction of motion. Since there is no horizontal force on the pencil, its horizontal motion

doesn’t change.

CONCEPTUAL PHYSICS

Chapter 3 Newton’s First Law of Motion—Inertia 11

Name Class Date

Inertia

Circle the correct answers.

1. An astronaut in outer space away from gravitational or frictional forces throws a rock. The rock will

(gradually slow to a stop)

(continue moving in a straight line at constant speed).

The rock’s tendency to do this is called

(inertia) (weight) (acceleration).

2. The sketch shows a top view of a rock being whirled at

the end of a string (clockwise). If the string breaks, the

path of the rock is

(A) (B) (C) (D).

3. Suppose you are standing in the aisle of a bus that travels

along a straight road at 100 km/h, and you hold a pencil still

above your head. Then relative to the bus, the velocity of the

pencil is 0 km/h, and relative to the road, the pencil has a

horizontal velocity of

(less than 100 km/h) (100 km/h) (more than 100 km/h).

Suppose you release the pencil. While it is dropping, and rela-

tive to the road, the pencil still has a horizontal velocity of

(less than 100 km/h) (100 km/h) (more than 100 km/h).

This means that the pencil will strike the ﬂ oor at a place directly

(behind you) (at your feet below your hand) (in front of you).

Relative to you, the way the pencil drops

(is the same as if the bus were at rest)

(depends on the velocity of the bus).

How does this example illustrate the law of inertia?

3-2

Concept-Development

Practice Page

Name ___________________________ Class __________________ Date ____________

Chapter 1 About Science

Conceptual Physics Reading and Study Workbook

N

Chapter 1 3

Exercises

1.1 The Basic Science—Physics (page 1)

1. The study of science today branches into the study of the

sciences and the sciences.

2. Write L or P beside each of the following to classify it as a branch of life

science or physical science.

zoology astronomy

physics botany

chemistry geology

biology

3. Complete the following table by identifying each type of science described.

Type of Science Description

The study of the nature of things such as motion, forces, energy,

matter, heat, sound, light, and the composition of atoms

The study of how matter is put together, how atoms combine

to form molecules, and how the molecules combine to make up

matter

The study of matter that is alive

1.2 Mathematics—The Language of Science (page 1)

4. When the ideas of science are expressed in mathematical terms, they are

5. Explain why equations are often used in science.

6. Is the following sentence true or false? Scientific findings are harder

to verify or to disprove when they are expressed mathematically.

1.3 Scientific Methods (page 2)

7. Which two scientists are usually credited as the principal founders of the

scientific method?

and

8. Name five steps that are generally included in scientific methods.

life

physical

Physics

Chemistry

Biology

unambiguous

Equations provide compact expressions of relationships between concepts.

false

Francis Bacon

Galileo Galilei

Make an educated guess—a hypothesis—about the answer.

Formulate the simplest general rule that organizes the main ingredients: hypothesis, prediction,

and experimental outcome.

Recognize a problem.

Predict the consequences of the hypothesis.

Perform experiments to test predictions.

Name ___________________________ Class __________________ Date ____________

Chapter 1 About Science

4 Conceptual Physics Reading and Study Workbook

N

Chapter 1

9. Is the following statement true or false? Following the steps of the

scientific method exactly is an important part of the success of science.

1.4 The Scientific Attitude (pages 2–3)

Match each term to its definition.

Term Definition

10. law or principle

11. fact

12. hypothesis

13. What should happen if a scientist finds evidence that contradicts a hypothesis,

law, or principle?

14. Which is more reliable, an idea of a scientist who has an excellent reputation or a

single verifiable experiment that shows the idea is wrong?

15. In everyday speech, the word theory means

16. In science, the word theory means

17. Is the following statement true or false? Once an idea becomes a theory, it cannot

be changed.

1.5 Scientific Hypotheses (page 4)

18. What must be true in order for a hypothesis to be scientific?

19. To determine whether a hypothesis is scientific or not, you should

20. Scientists perform a(n)

to test a(n) .

21. Is the following hypothesis scientific? Why? “Intelligent life exists on other planets

somewhere in the universe.”

a. a close agreement by competent observers

who make a series of observations of the same

phenomenon

b. a hypothesis that has been tested over and over

again and not contradicted

c. an educated guess that is not fully accepted until

demonstrated by experiment

The hypothesis, law, or principle must be changed or abandoned.

a single verifiable experiment that shows the idea is wrong

a supposition that has not been verified

a synthesis of a large body of information that

encompasses well-tested and verified hypotheses about certain aspects of the natural world

false

The hypothesis must be testable.

look to see if there is a test for proving it wrong

experiment

scientific hypothesis

No; there is no test for proving it wrong.

false

Name ___________________________ Class __________________ Date ____________

Chapter 1 About Science

Conceptual Physics Reading and Study Workbook

N

Chapter 1 5

1.6 Science, Technology, and Society (page 5)

22. Science is a method of answering ; technology is a method of

solving

23. Write S or T to indicate whether the following statements describe science or

technology.

Involves the design and creation of something for the use and enjoyment of

humans

Has to do with discovering facts and relationships between observable

phenomena in nature

1.7 Science, Art, and Religion (page 6)

Match each term to its definition.

Term Definition

24. science

25. art

26. religion

27. The domain of science is

; the domain of religion is

1.8 In Perspective (page 7)

28. Is the following statement true or false? Progress was much slower thousands of

years ago than it is today.

29. Thousands of years ago, the building of great structures such as the Pyramids was

inspired by

30. Is the inspiration for progress today similar to or different from the inspiration

thousands of years ago?

a. concerned with the source, purpose, and

meaning of everything

b. concerned with the value of human interactions

as they pertain to the senses

c. concerned with discovering and recording

natural phenomena

natural order

nature’s purpose

true

a vision of the cosmos

similar to

theoretical questions

practical problems

Name ___________________________ Class __________________ Date ____________

Chapter 2 Mechanical Equilibrium

Conceptual Physics Reading and Study Workbook

Chapter 2 9

Exercises

2.1 Force (pages 13–14)

1. A force is a or a .

2. A force is needed to change the state of

of an

object.

3. Is the following sentence true or false? If an object is sliding on ice, it will

continue sliding until a force slows it down.

4. Define net force.

Match the applied forces on an object with the letter of the corresponding net

force on the object.

Applied Forces Net Force

5. 5 N to the right and5Ntotheleft a. 2 N to the left

6. 4 N to the right and6Ntotheleft b. 2 N to the right

7. 7 N to the right and5Ntotheleft c. 10 N to the right

8. 6 N to the right and4Ntotheright d. 0 N (no change in motion)

9. Describe the forces that act on a rock at rest in your hand.

10. Circle the letter that identifies the force acting upward on an object

suspended from a spring scale.

a. gravity b. equilibrium

c. tension d. weight

11. A

is an arrow that represents the magnitude and

direction of a quantity.

12. Explain the difference between a vector quantity and a scalar quantity.

13. Write V beside each vector quantity. Write S beside each scalar quantity.

a. time b. area

c. force d. volume

push

pull

motion

true

the combination of all forces acting on an object

Your hand pushes upward on the rock with as much force as Earth’s gravity pulls down

on it.

vector

A vector quantity is a quantity that describes both magnitude and direction. A scalar

quantity can be described by magnitude only and has no direction.

Name ___________________________ Class __________________ Date ____________

Chapter 2 Mechanical Equilibrium

10 Conceptual Physics Reading and Study Workbook

Chapter 2

2.2 Mechanical Equilibrium (page 16)

14. Express the equilibrium rule in words.

15. Express the equilibrium rule mathematically, and explain what the

symbol in the rule means.

16. Circle the letter that describes the forces acting on a suspended object

at rest.

a. The forces acting upward on the object are greater than the

forces acting downward on the object.

b. The forces acting upward on the object are less than the forces

acting downward on the object.

c. The forces acting upward and downward on the object are

balanced.

d. No forces are acting on the object.

2.3 Support Force (page 17)

17. Identify the two forces acting on a book at rest on a table. State the

direction of each force.

18. The force is the upward force that balances the

weight of an object on a surface. Another name for this force is the

force.

19. Look at the drawing above. Explain how the force of the table

pushing up on the book is similar to what happens when the spring is

compressed.

The weight of the book due to gravity acts downward.

Whenever the net force on an object is zero, the object is said to be in mechanical

equilibrium.

¤F = 0; the symbol ¤ means “the sum of.”

The support force provided by the table acts upward on the book.

normal

support

When the spring is compressed, it pushes upward on your hand. Similarly, the book

sitting on the table compresses the atoms of the table. The atoms then push upward on

the book.

Name ___________________________ Class __________________ Date ____________

Chapter 2 Mechanical Equilibrium

Conceptual Physics Reading and Study Workbook

Chapter 2 11

20. Circle the letter that describes an object at rest on a horizontal surface.

a. The support force is equal to the object’s weight.

b. The support force is greater than the object’s weight.

c. The support force is less than the object’s weight.

2.4 Equilibrium for Moving Objects (pages 18–19)

21. If an object is moving at a speed in a

path, it is in a state of equilibrium.

22. Is the following sentence true or false? If a desk is pushed at a

constant speed across a horizontal floor, the force of friction

must be equal in magnitude and opposite in direction to the pushing

force on the desk.

23. Objects at rest are said to be in equilibrium.

24. Objects moving at constant speed in a straight-line path are said to be in

equilibrium.

2.5 Vectors (pages 19–22)

25. Suppose a gymnast with a weight of 300 N is suspended by a single

vertical rope. What is the tension in the rope?

26. Now suppose the same gymnast hangs from two vertical ropes. What

are the tensions in the ropes?

27. Define resultant.

28. State the parallelogram rule.

29. The gymnast shown below is suspended from two non-vertical ropes.

The solid vector represents the gymnast’s weight. What does the dashed

vector represent?

straight-line

constant

True

static

dynamic

300 N

150 N in each rope

the sum of two or more vectors

To find the resultant of two vectors, construct a parallelogram wherein the two vectors

are adjacent sides. The diagonal of the parallelogram shows the resultant.

the resultant of the tensions in both ropes

Name ___________________________ Class __________________ Date ____________

Chapter 3 Newton’s First Law of Motion—Inertia

Conceptual Physics Reading and Study Workbook

Chapter 3 15

Exercises

3.1 Aristotle on Motion (pages 29–30)

Fill in the blanks with the correct terms.

1. Aristotle divided motion into two types:

and

2. Natural motion on Earth was once thought to be either

or .

3. Aristotle thought that it was natural for heavy things to

and for light things to .

4. Aristotle also thought that

motion was natural for

objects beyond Earth and that the planets and stars moved in perfect

circles around

5. What force was thought to have caused a horse and cart to experience

violent motion?

6. Before the 1500s, the proper state of objects was thought to be one of

, unless they were being pushed or pulled or were

moving toward their natural resting place.

7. Is the following statement true or false? Early thinkers thought that

violent motion was imposed motion.

8. Is the following statement true or false? It was commonly thought by

many ancient thinkers that if an object moved “against its nature,” then

a force of some kind was responsible.

3.2 Copernicus and the Moving Earth (page 30)

Determine if each of the following statements is true or false.

9. Copernicus thought that Earth and other planets move

around the sun.

10. Copernicus thought that Earth was at the center of the

universe.

11. Copernicus did not publish his ideas until he was near

death.

12. Copernicus lived a long and happy life after his works

were published.

13. Why did Copernicus do most of his work in secret?

3.3 Galileo on Motion (pages 30–32)

14. What was one of Galileo’s great contributions to physics?

15. A force is any or .

natural motion

straight down

fall

violent motion

straight up

rise

circular

Earth

the pull of the horse

rest

true

false

Copernicus’ ideas were very controversial, so he worked in secret to avoid persecution.

demolishing the notion that a force is necessary to keep an object moving

push

pull

Name ___________________________ Class __________________ Date ____________

Chapter 3 Newton’s First Law of Motion—Inertia

16 Conceptual Physics Reading and Study Workbook

Chapter 3

16. Explain what friction is and how it acts.

17. In the drawings below, describe each type of slope on the top line. On

the bottom line, describe the slope’s affect on speed.

a. b. c.

18. Based on his experiments with rolling balls, Galileo was able to conclude

that when friction is present, a

is needed to keep

an object moving.

19. Describe the property of inertia in your own words.

3.4 Newton’s Law of Inertia (pages 33–35)

20. What is another name for Newton’s first law of motion?

21. State Newton’s first law of motion.

22. Use Newton’s first law of motion to explain what happens to dishes on a

table when the tablecloth is quickly pulled from beneath them.

23. Objects in a state of rest tend to remain at rest; only a

will change that state.

24. Use Newton’s first law of motion to explain why an air hockey puck

slides on the game table with no apparent loss in speed. Name two

things that can cause the puck to change its state of motion.

25. Once an object is moving in a force-free environment, for how long will

it move in a straight line?

Friction is the force that acts between materials that touch as they move past each other.

Friction is caused by irregularities in the surfaces that are touching. All irregularities

obstruct motion causing a force (friction) that opposes motion.

Slope downward

Speed increases

Slope upward

Speed decreases

No slope

Speed does not change

force

A body in motion will stay in motion unless acted on by a force. Likewise, a body at rest

will stay at rest unless acted on by a force. Or, every object resists change to its state of

motion.

the law of inertia

Newton’s first law states that every object continues in a state of rest, or of uniform

speed in a straight line, unless it is acted on by a nonzero net force.

Dishes on a tabletop are at rest. They tend to remain at rest even when the tablecloth is

pulled from beneath them because friction between the dishes and the tablecloth is not

significant enough to move the dishes very much.

force

In the absence of forces, a moving object such as the air hockey puck will move

indefinitely in a straight line. The puck will change its motion if it is struck or if it hits the

side of the playing table.

indefinitely

Name ___________________________ Class __________________ Date ____________

Chapter 3 Newton’s First Law of Motion—Inertia

Conceptual Physics Reading and Study Workbook

Chapter 3 17

3.5 Mass—A Measure of Inertia (pages 36–38)

26. Circle the letter of each sentence that is true about the mass of an object.

a. The amount of inertia an object has depends on its mass.

b. The more mass an object has, the greater its inertia.

c. Volume and mass are the same quantity.

d. Mass is usually measured in kilograms.

27. Which item below has more mass? Which has more volume? Which has

the greater inertia?

28. Is the following sentence true or false? Mass is a measure of the

gravitational force acting on an object.

29. is a measure of the amount of material in an object

and depends on the number of and kind of atoms that compose it.

30. Is the following sentence true or false? A stone has the same mass

on Earth and on the moon, but its weight is less on the moon.

31. is the quantity of matter in an object.

32.

is the force of gravity on an object.

Match each phrase with the correct word.

Phrase Word

33. traditional unit of weight

in the United States

34. measure of matter in most

parts of the world

35. SI unit of mass

36. SI unit of force

3.6 The Moving Earth Again (pages 38–39)

37. If Earth is rotating at 30 km/s, explain how a bird sitting on a tree can

drop down vertically and grab a worm that is crawling on the ground.

a. kilogram

b. mass

c. pound

d. newton

The battery has greater mass and thus greater inertia. The pillow has greater volume.

false

Mass

true

Mass

Weight

Earth, the bird, the tree, the ground, and the worm are all rotating as one unit. Because

everything is rotating as one unit, Earth’s rotation does not affect the bird’s ability to

descend vertically to grab the worm.

Name ___________________________ Class __________________ Date ____________

Chapter 3 Newton’s First Law of Motion—Inertia

18 Conceptual Physics Reading and Study Workbook

Chapter 3

38. A girl is sitting on a bus that is traveling at 30 km/h. She is throwing her

tennis ball gently into the air and catching it. Circle the letter of each true

statement.

a. The tennis ball is moving faster than the girl riding on the bus.

b. The tennis ball is behaving as if the bus were at rest.

c. The inertia of the tennis ball changes when it is thrown.

d. Gravity affects only the vertical motion of the tennis ball.

Match the ideas on motion with the correct scientist.

Idea Scientist

39. did not recognize inertia

40. developed the law of inertia

41. believed that horizontal motion

was “unnatural”

42. was one of the first to recognize

that no force was needed to keep

an object in motion

a. Aristotle

b. Newton

c. Galileo