Lesson 1 | Gravity and Friction



Lesson 1 | Gravity and Friction

|Student Labs and Activities |Page |Appropriate For: |

|Launch Lab |8 |all students |

|Content Vocabulary |9 |all students |

|Lesson Outline |10 |all students |

|MiniLab |12 |all students |

|Content Practice A |13 |[pic] |

|Content Practice B |14 | [pic] |

|School to Home |15 |all students |

|Key Concept Builders |16 |[pic] |

|Enrichment |20 |all students |

|Challenge |21 | [pic] |

|Assessment | | |

|Lesson Quiz A |22 |[pic] |

|Lesson Quiz B |23 | [pic] |

| | | |

| | | |

|[pic] |Approaching Level |[pic] |On Level |[pic] |Beyond Level |[pic] |English-Language Learner |

Teacher evaluation will determine which activities to use or modify to meet any student’s proficiency level.

The Laws of Motion 7

Name Date Class

LESSON 1: 5 minutes

Can you make a ball move without touching it?

You can make a ball move by kicking it or throwing it. Is it possible to make the ball move

even when nothing is touching the ball?

Procedure

1. Read and complete a lab safety form.

2. Roll a tennis ball across the floor.

Think about what makes the ball move.

3. Toss the ball into the air. Watch as it

moves up and then falls back to your

hand.

4. Drop the ball onto the floor. Let it

bounce once, and then catch it.

Think About This

1. What made the ball move when you rolled, tossed, and dropped it? What made it stop?

2. Key Concept Did something that was touching the ball or not touching the ball

cause it to move in each case?

8 The Laws of Motion

Name Date Class

LESSON 1

Gravity and Friction

Directions: Use the clues and the terms listed below to complete the puzzle. NOTE: There is no empty square in

the puzzle between the words of two-word terms.

|contact force |force |friction |gravity |mass |

|noncontact force |significant |static |weight | |

Clues

Across

6. the amount of matter in an object

9. Gravity is an example of this kind

of force.

Down

1. a force that resists the motion of two

surfaces that are touching

2. the gravitational force exerted on an

object

3. an attractive force that exists between

all objects that have mass

4. at rest

5. important

7. a push or pull on an object by another

object that is touching it

8. a push or a pull

The Laws of Motion 9

Name Date Class

LESSON 1

Gravity and Friction

A. Types of Forces

1. A push or a pull is called a(n) .

2. A(n) is a push or a pull on an object by another object

that is touching it.

3. A force that one object can apply to another object without touching it is

a(n) .

4. Gravity, , and electric forces are examples of

noncontact forces.

5. Forces have and

6. An arrow can be used to show a force; the shows the

strength of the force, and the direction of the arrow shows the

of the force.

7. Forces are measured in units called .

B. What is gravity?

1. is the amount of matter in an object.

2. is an attractive force that exists between all objects that

have mass.

3. Mass is often measured in .

4. According to the law of , all objects are attracted to one

another with a gravitational force that is proportional to the mass of the objects

and the distance between them.

a. When the mass of one or both objects increases, the gravitational force between

the objects .

b. When the distance between two objects increases, the attraction between the

objects .

5. is the gravitational force exerted on an object.

a. Near Earth’s surface, an object’s weight is the gravitational force exerted on the

object by .

b. The of an object on Earth decreases significantly only

when the object moves a great distance away from Earth.

10 The Laws of Motion

Name Date Class

Lesson Outline continued

C. Friction

1. is a force that resists the motion of two surfaces that are

touching.

2. friction prevents surfaces from sliding past each other.

3. Up to a limit, the of static friction changes to match

the applied force.

4. friction opposes the motion of surfaces sliding past

each other.

a. When an object is sliding, the force of sliding friction does not

; for this reason, increasing the applied force makes

a sliding object move .

b. If you stop pushing a sliding object, the object will eventually

due to sliding friction.

5. is friction between a surface and a fluid, such as air

or water.

a. Fluid friction between an object and air is called .

b. Decreasing an object’s surface area by changing its shape

the object’s air resistance.

6. One reason for friction between surfaces is the , or the

dips and bumps on one surface that catch on those of the other surface.

7. One reason for friction between surfaces is that atoms and molecules with

charges attract each other.

8. decrease friction by causing a slight separation between

solid surfaces, so they don’t contact each other.

The Laws of Motion 11

Name Date Class

LESSON 1: 10 minutes

How does friction affect motion?

Friction affects the motion of an object sliding across a surface.

Procedure

1. Read and complete a lab safety form.

2. Use tape to fasten sandpaper to a

table. Attach a spring scale to a

wooden block with an eyehook in it.

3. In the Data and Observations below,

record the force required to gently pull

the block at a constant speed on the

sandpaper and then on the table.

Data and Observations

Analyze and Conclude

1. Compare the forces required to pull the block across the two surfaces.

2. Key Concept How did reducing friction affect the motion of the block?

12 The Laws of Motion

Name Date Class

LESSON 1

Gravity and Friction

Directions: On the line before each definition, write the letter of the term that matches it correctly. Each term is

used only once.

1. a push or a pull on an object

2. push or pull on one object by another object

3. applied without touching

4. makes hair stand on end

5. keeps you from floating away

6. makes a compass needle point north

7. unit of mass

8. unit of force or weight

9. resists the motion of two surfaces that are

touching

10. reduces friction

A. noncontact force

B. friction

C. electric force

D. gravity

E. lubricant

F. force

G. newton

H. contact force

I. magnetic force

J. kilogram

The Laws of Motion 13

Name Date Class

LESSON 1

Gravity and Friction

Directions: Answer each question or respond to each statement on the lines provided.

1. Define the terms below.

a. force

b. contact force

c. noncontact force

2. What are three noncontact forces?

3. What are the units for mass and weight?

4. What is the difference between mass and weight?

5. Explain how the gravitational force between two objects is affected by their mass and

the distance between them.

6. What is friction?

7. What are the three kinds of friction discussed in the lesson?

14 The Laws of Motion

Name Date Class

LESSON 1

Gravity and Friction

For this activity, you will need a small object that you can slide across a surface, such as a

bottle cap or a coin. You will also need a ruler or a measuring tape and a pencil.

|Surface |Distance Traveled by Object (cm) |

| |Prediction |Trial 1 |Trial 2 |Trial 3 |

| | | | | |

| | | | | |

| | | | | |

| | | | | |

1. Locate four flat surfaces in or around your home that would exert different amounts

of friction on a sliding object. Record the surfaces in the Surface column. Examples of

surfaces include a carpeted floor, a tile floor, and a glass tabletop.

2. Predict how much friction each surface will exert on an object sliding across it. In the

Prediction column, rank the surfaces from 1 to 4. Write 1 for the surface you expect to

exert the most friction and 4 for the surface you expect to exert the least.

3. Push the object across the first surface three different times. Use the ruler to measure

the distance it slides during each trial and record each distance in the table. Try to

apply the same amount of force each time. Repeat this step for each surface.

4. Which surface exerted the most friction on the object? How do you know?

5. Did you correctly predict which surface would exert the most and least friction on the

object? Explain.

The Laws of Motion 15

Name Date Class

LESSON 1

Gravity and Friction

Key Concept What are some contact forces and some noncontact forces?

Directions: On the line before each motion, write C if it is caused by a contact force or N if it is caused by

a noncontact force.

1. rain falling

2. papers scattered by wind

3. a baseball sailing into the outfield

4. a magnet attracting a nail

5. rocks tumbling down a mountain

6. an elevator ascending

7. an arrow flying toward a target

8. lightning striking a building

9. a brick wall collapsing

10. a meteorite hitting Earth

Directions: Answer each question on the lines provided.

11. What is a force?

12. What is a contact force?

13. What is a noncontact force?

14. What is the unit of force?

16 The Laws of Motion

Name Date Class

LESSON 1

Gravity and Friction

Key Concept What is the law of universal gravitation?

This diagram represents a star orbited by two planets—planet A and planet B. The star is

also orbited by a mysterious object, object X, that entered into the star’s gravitational field.

Directions: Use the diagram to answer each question or respond to each statement.

1. The gravitational force between the star and planet A is the same as the gravitational

force between the star and planet B. Explain why this is true.

2. The gravitational force between the star and object X is equal to the forces between the

star and the two planets. From that information, what can you conclude about object X?

Directions: Answer each question on the lines provided.

3. What is gravity?

4. What happens to the gravitational attraction between two objects as the distance

between them increases?

The Laws of Motion 17

Name Date Class

LESSON 1

Gravity and Friction

Key Concept What is the law of universal gravitation?

Directions: Complete this concept map by choosing terms from the word bank and writing them in the correct spaces.

effect force gravity mass newton object unit

Directions: On the line before each statement, write T if the statement is true or F if the statement is false.

8. An object that has twice as much mass as another weighs four times as much.

9. Near Earth’s surface, the weight of an object in newtons is about 10 times its

mass in kilograms.

10. The weight of an astronaut in orbit is about 90 percent of the astronaut’s

weight on Earth.

18 The Laws of Motion

Name Date Class

LESSON 1

Gravity and Friction

Key Concept How does friction affect the motion of two objects sliding past each other?

Directions: On each line, write the term from the word bank that correctly completes each sentence. Each term is

used only once.

electrical fluid lubricants microscopic

movement resistance sliding static

1. Friction is a force that opposes .

2. To push a heavy crate across a floor, you must first overcome

friction, which tends to hold it in place.

3. After overcoming that form of friction, you must push against

friction.

4. Friction between a surface and air or a liquid is called

friction.

5. Air friction on a car or airplane is also called air .

6. Friction between solid surfaces is caused mostly by roughness on a(n)

scale.

7. Friction can also be caused by attraction between particles.

8. Friction between solid surfaces can be reduced with

The Laws of Motion 19

Name Date Class

LESSON 1

Force at a Distance

Lobsters know their way home, and

researchers who studied lobster behavior

believe it is due to Earth’s magnetic field.

Earth’s Magnetic Field

Scientists think that Earth’s magnetic

field is produced by the movement of

electric charges in Earth’s core. The core is

mostly iron and nickel; the inner core is

solid because of the great pressure at that

level, but in the outer core, the metals are

liquid because there is less pressure. As

Earth rotates, the liquid in the core flows

and electric charges move, creating the

magnetic field. As the field travels outward

through the rest of Earth’s interior, the field

lines extend from Earth near Antarctica and

enter again near Canada.

Earth’s magnetic field acts like a giant

bar magnet. It has two poles—north and

south. When you put unlike poles together,

you can feel magnetic attraction. Like poles

of a bar magnet repel each other.

In the northern hemisphere, when a

compass needle points north, we use it as a

tool to find a direction. However, because

the north-pointing magnetism of the

compass needle can be attracted only by

the south pole of a magnet, the magnetic

pole in the northern hemisphere has a

south polarity. It follows that magnetic

north is at the geographic South Pole.

Going Home

Results of the lobster-behavior study

are illustrated below. Researchers moved

one group of lobsters (squares) from their

home at catch site 1 to the test site

southwest of their home. They moved

another group (circles) from their home at

catch site 2 to the test site that was

northeast of their home.

The lobsters were placed in opaque

containers and transported by boat along

circuitous routes of up to 30 km; then they

were released at the test site. The next day,

the lobsters were discovered positioned

facing the catch site and walking in the

direction indicated in the figure.

The researchers concluded that their

results demonstrated that an invertebrate

animal is capable of true navigation based

upon Earth’s magnetic field.

Applying Critical-Thinking Skills

Directions: Answer each question.

1. Relate Look up pictures of the Aurora Borealis (Northern Lights) and the Aurora

Australis (Southern Lights). What are they? Why do they occur?

2. Interpret In which directions were the CS1 and CS2 lobsters walking on the second

day of the lobster study?

20 The Laws of Motion

Name Date Class

LESSON 1

Air Resistance by Design

Many common objects in daily use today were designed to increase or decrease air

resistance. Choose one of the following activities, A or B.

A. Model

1. Research the design, use, and construction of parachutes.

2. Diagram a common parachute design. Construct a full-sized model out of old

newspaper or other scrap material. Display the model in your classroom. Perhaps it can

hang from the ceiling.

3. Write a sentence or two describing the function a parachute serves for a parachutist.

B. Classify

1. On separate index cards or pieces of paper, diagram your observations of the design of

20 vehicles parked or traveling in the neighborhood of your home or school.

2. Group the diagrams into three different classifications, based on their shapes. Name

the three groups.

3. Write a sentence or two describing the relationship between the shape of a vehicle and

its performance.

The Laws of Motion 21

Name Date Class

LESSON 1

Gravity and Friction

True or False

Directions: On the line before each statement, write T if the statement is true or F if the statement is false.

1. Gravity and magnetism are examples of contact forces.

2. Weight is the measure of gravitational force on an object.

3. Mass and weight are not related to each other.

4. Forces have strength and direction.

Multiple Choice

Directions: On the line before each question or statement, write the letter of the correct answer.

5. You can reduce friction by

A. increasing mass.

B. removing lubricant.

C. reducing surface area.

6. Which type of friction exists between a surface and moving air?

A. fluid friction

B. static friction

C. sliding friction

7. Which factor is NOT involved in determining gravitational force?

A. mass

B. speed

C. distance

8. A is NOT a force.

A. fall

B. pull

C. push

22 The Laws of Motion

Name Date Class

LESSON 1

Gravity and Friction

Completion

Directions: On each line, write the term that correctly completes each sentence.

1. Gravity and magnetism are examples of forces.

2. is the measure of gravitational force on an object.

3. An object’s weight is proportional to its .

4. Forces have strength and .

Short Answer

Directions: Respond to each statement on the lines provided.

5. State two ways to reduce friction on an object.

6. Recall the three types of friction and explain how each acts on objects.

7. Assess what determines the strength of gravitational force between two objects.

8. Determine what is needed to exert a force.

The Laws of Motion 23

-----------------------

Launch Lab

Content Vocabulary

Lesson Outline

MiniLab

Content Practice A

Content Practice B

School to Home

Did you know?

Friction is a contact force between two surfaces that are touching. If the surfaces

slide against each other with little resistance, the force of friction is weak. Only a

weak force is needed to make the object move. If the surfaces slide against each

other with a strong resistance, then the force of friction is strong, and a stronger

force will be required to make the objects move.

Key Concept Builder

Key Concept Builder

Key Concept Builder

Key Concept Builder

Enrichment

Challenge

Lesson Quiz A

Lesson Quiz B

Weight

is a(n)

is the

of

and is measured in a(n)

on the

called the

of a(n)

1.

2.

3.

4.

8.

7.

6.

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