Lesson 3 | Simple Machinesimages.pcmac.org/SiSFiles/Schools/AL/SatsumaSchools/SatsumaHigh... · 5. A(n) is a simple machine that is a ... Read and complete a lab ... There are a total

Work and Simple Machines 47

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Lesson 3 | Simple Machines

Student Labs and Activities Page

Launch Lab 48

Content Vocabulary 49

Lesson Outline 50

MiniLab 52

Content Practice A 53

Content Practice B 54

Language Arts Support 55

School to Home 57

Key Concept Builders 58

Enrichment 62

Challenge 63

Lab A 66

Lab B 69

Lab C 72

Chapter Key Concepts Builder 73

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48 Work and Simple Machines

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Launch Lab LESSON 3: 15 minutes

How does a lever work?Humans have used levers for thousands of years to make work easier. How does a lever change the force applied to it?

Procedure 1. Read and complete a lab safety form.

2. Place a ruler on top of an eraser, as shown in your textbook. Place a bookon one end of the ruler.

3. Lift the book by pushing down on the other end of the ruler. Record in the

Data and Observations

Think About This 1. Explain how changing the position of the eraser affected the force exerted by the lever.

2. Key Concept How would you describe the motion of the lever? Is the motion of the lever simple or complicated? Explain.

Data and Observations section below how easy or difficult it is to lift the book.

4. Repeat steps 2 and 3 several times using different locations of the eraser

along the ruler.

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Simple MachinesDirections: Complete the chart by providing at least one example for each item below.

Give an example of . . . Examples

a simple machine. 1.

an inclined plane. 2.

a lever. 3.

something that acts as a fulcrum. 4.

something a screw is used to do. 5.

a wheel and axle. 6.

a wedge. 7.

a pulley. 8.

Content Vocabulary LESSON 3



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Simple Machines A. What is a simple machine?

1. A(n) is a machine that does work using only one movement.

2. These machines do work in a(n) motion.

B. Levers

1. A(n) is a simple machine made of a bar that pivots or rotates about a fixed point.

2. The point that a lever pivots on is called a(n) .

3. The distance from the fulcrum to the input force is the

; the distance from the fulcrum to the output

force is the .

4. With a first-class lever, the fulcrum is the input force and the output force.

5. With a second-class lever, the force is between the

force and the fulcrum.

6. With a third-class lever, the force is between the

force and the fulcrum.

7. The ideal of a lever equals the length of the input arm divided by the length of the output arm.

a. The mechanical advantage of a(n) -class lever can vary, depending on the location of the fulcrum.

b. In a second-class lever, the arm is always longer than

the arm.

c. In a third-class lever, the arm is always shorter than

the arm.

8. In the human body, provide force for the levers.

a. The neck is a(n) -class lever, with the neck muscles

providing the force.

b. The foot is a(n) -class lever, and the arm is a(n)

-class lever.

Lesson Outline LESSON 3



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Lesson Outline continued

C. Wheel and Axle

1. A(n) is an axle attached to the center of a wheel and both rotate together.

2. For a wheel and axle, the length of the input arm is the

of the wheel; the length of the output arm is the of the axle.

D. Inclined Planes

1. A(n) is a flat, sloped surface.

2. The ideal mechanical advantage of an inclined plane is the

of the inclined plane divided by

its .

3. A sloped surface that moves is called a(n) .

4. A(n) is an inclined plane wrapped around a cylinder.

5. A(n) is a simple machine that is a grooved wheel with a rope or cable wrapped around it.

6. A(n) pulley only changes the direction of the force.

7. A(n) pulley decreases the force but increases the distance over which the force acts.

8. The ideal mechanical advantage of a pulley is equal to the number of

of rope pulling up on the object.

E. What is a compound machine?

1. Two or more simple machines that operate together form a(n)

machine.

2. A(n) is a wheel and axle that has teeth around the wheel.

3. When the teeth of two or more gears , the turning of one gear makes the other(s) turn.

4. The speed and force of gears is affected by the of the gears.

5. The efficiency of a compound machine is determined by

the efficiency of each component machine together.



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LESSON 3: 20 minutes

Can you increase mechanical advantage?Pulley systems change the size and the direction of an applied force. How can you change the mechanical advantage of a pulley system?


2. Use two broomsticks and an 8-m length of rope to make a pulley system, as shown in your textbook. Hold each broomstick waist-high. Tie the rope to one of the broomsticks and loop it around the other.

Data and Observations

Analyze and Conclude 1. Describe how the force applied on the broomsticks changed when the number of

loops in the pulley system increased.

2. Key Concept Relate the number of rope segments used in each pulley system to the mechanical advantage of each system.

3. Have a student pull the free end of the rope, as shown in your textbook. Record in the space below the forces acting on the broomsticks.

4. Take the excess rope and make two more loops around the broomsticks. Repeat step 3.

MiniLab



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LESSON 3

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

1. There are a total of three types of simple machines.

2. A lever consists of a bar that pivots about a fixed point called the focus.

3. There are four classes, or kinds, of levers.

4. The mechanical advantage of a second-class lever is always less than 1.

5. The forearm of the human body works like a third-class lever.

6. The length of a wheel’s input arm is the diameter of the wheel.

7. The purpose of a ramp, which is a type of inclined plane, is to make it easier to move a heavy object over a vertical distance.

8. A wedge is a sloped surface that forces materials apart.

9. When you turn a screw into a piece of wood, the input force of the screwdriver is converted to an output force by the threads of the screw.

10. A combination of fixed and movable pulleys working together is called a pulley system.

11. When two or more simple machines work together, it is called a composite machine.

12. The efficiency of such a machine is determined by multiplying the efficiencies of each simple machine.

Content Practice A



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LESSON 3

Simple MachinesDirections: Answer each question on the lines provided.

1. What is a simple machine, and what are the six types of simple machines?

2. Which factors determine whether a lever is a first-class lever, second-class lever, or third-class lever?

3. How does the MA of a 6-m ramp compare with the MA of a 4-m ramp if both are used to load crates onto trucks that have cargo areas that are 1 m off the ground?

4. What is a compound machine?

5. How does the input force applied by a large gear change when the force is applied to a smaller gear?

6. How do you calculate the overall efficiency of a compound machine?

Content Practice B



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Language-Usage Activity: Using Its and It’s A common error in writing is using the word it’s when the correct word is its.

Its is the possessive form, meaning “belonging to it.”

The model of the mountain did not match its actual shape.

It’s is a contraction of the word it and the word is.

It is wider in the middle.

It’s wider in the middle.

If you are unsure of which word to use, substitute it is in the sentence. If it makes sense, use it’s.

Practicing the SkillDirections: Circle the correct form of the word that completes each sentence.

1. You probably have heard of a seesaw. (It’s/Its) one of three kinds of levers.

2. A first-class lever has (its/it’s) fulcrum between the input force and the output force.

3. For a second-class lever, (its/it’s) location is different. The output force is between the

fulcrum and the input force.

4. A piece of luggage that has wheels is a second-class lever. (It’s/Its) easier to roll luggage

than to carry it.

5. Do you know where the input force is applied in a third-class lever? (Its/It’s) between

the fulcrum and the output force.

6. I have used a shovel, and (its/it’s) the same as using a third-class lever.

LESSON 3Language Arts Support

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Language-Usage Activity: Subject-Verb AgreementVerbs and their subjects must agree in number.

Singular Subjects Plural Subjects

A lever is a simple machine. Levers and wedges are simple machines.Subject: lever—singular Subject: Levers and wedges—pluralVerb: is—singular Verb: are—plural

In the present tense, verbs with the subject he, she, or it must end with –s. To test whether the subject and verb agree:

1. Find the subject of the sentence.

2. Ask yourself whether the subject is singular or plural.

3. Find the verb in the sentence.

4. Ask yourself whether the verb is in the singular or plural form.

If the subject and verb are both singular or both plural, they agree.

The –s Rule: In general, if the subject ends in –s, the verb cannot end in –s.

The dog barks. The dogs bark.

Applying the Skill Directions: Write YES on the line before each sentence if its subject and verb agree. Write NO if the subject and verb do not agree. If the subject and verb do not agree, write the correct form of the verb on the line after each sentence.

1. Your front tooth is an example of a wedge.

2. An axe also works as a wedge.

3. The fulcrum are the pivot point of the lever.

4. Two forces acts on a lever—the input force and the output force.

5. Your forearm work like a third-class lever.

6. Six types of simple machines are used.

7. The lengths of the input and output arms are important for calculating the

ideal mechanical advantage of a lever.

8. When you turn a screw, the output force pull the screw into the material.

Language Arts Support LESSON 3

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School to Home LESSON 3

Simple Machines

Did you know?Simple machines fall into two categories—the wedge family and the lever family. The wedge family includes the wedge, screw, and inclined plane. Screws and inclined planes are a variation on wedges. The lever family includes the lever, pulley, and wheel and axle. Pulleys and wheel and axles are a variation on levers.

For this activity, list three examples of each type of simple machine that you might see in your home or neighborhood.

Simple Machine Example 1 Example 2 Example 3

1. Wedge a. b. c.

2. Screw a. b. c.

3. Inclined plane a. b. c.

4. Lever a. b. c.

5. Pulley a. b. c.

6. Wheel and axle a. b. c.

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LESSON 3Key Concept Builder

Simple Machines Key Concept What is a simple machine?

Directions: On the line before each item, write L if it uses or is a lever, WH if it uses or is a wheel and axle, I if it uses or is an inclined plane, WE if it uses or is a wedge, S if it uses or is a screw, or P if it uses or is a pulley.

1. flagpole

2. wedge that splits wood

3. roller skates

4. crowbar

5. jar lid

6. nail

7. sailboat mast

8. truck-loading ramp

9. seesaw

10. doorknob

11. drill bit

12. nutcracker

13. wheelchair ramp

14. narrow bow of a ship

Directions: Define simple machine on the lines provided.

15.

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Key Concept Builder LESSON 3

Simple Machines

Key Concept What is a simple machine?

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 lever’s pivot point

2. a shaft that turns

3. a wheelbarrow

4. the part of a lever that applies force

5. a flat, sloped surface

6. a sloped surface that moves

7. a hockey stick

8. an inclined plane wrapped around a cylinder

9. an oar

10. good for vertical lifting

A. first-class lever

B. screw

C. second-class lever

D. pulley

E. wedge

F. fulcrum

G. input arm

H. third-class lever

I. inclined plane

J. axle



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LESSON 3Key Concept Builder

Simple MachinesKey Concept How is the ideal mechanical advantage of simple machines calculated?

Directions: Use the equations to answer each question on the lines provided.

1. What is the mechanical advantage of a lever that has an output arm measuring 0.5 m and an input arm measuring 1.5 m?

2. What is the mechanical advantage of a wheel that has a radius of 0.35 m, if the axle has a radius of 0.05 m?

3. What is the mechanical advantage of a ramp with a length of 5 m and a height of 1 m?

mechanical advantage of a lever = length of input arm (in meters) _______________________

length of output arm (in meters)

MA = Lin ____ Lout

mechanical advantage of a wheel and axle = radius of wheel (in meters) ___________________

radius of axle (in meters)

MA = rwheel ______ raxle

mechanical advantage of an inclined plane = length of inclined plane (in meters) _________________________

height of inclined plane (in meters)

MA = l __ h



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Key Concept Builder LESSON 3

Simple Machines

Key Concept How are simple machines and compound machines different?

Directions: Answer each question on the lines provided.

1. What is a compound machine?

2. How is the efficiency of a compound machine calculated?

3. What happens to the efficiency of the overall machine as more simple machines are added to it?

4. How can gears change the size and direction of a force?

5. Explain why a wedge that splits wood is an example of a compound machine.

6. Suppose the efficiency of the wedge portion of a wedge that splits wood is 90 percent (or 0.9) and the efficiency of the lever part of it is 80 percent (or 0.8). What is the efficiency of the machine?



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Sharks and Levers

Enrichment

Applying Critical-Thinking SkillsDirections: Respond to each statement.

1. Predict what will happen when the bicep muscle exerts force on the lower arm bone in Figure 1.

2. Describe the location of the fulcrum and the location of the load in Figure 2.

Bethany Hamilton is a courageous teenage girl who is a competitive surfer. In 2003, when she was 13 years old, Bethany lost her left arm in a shark attack near her home in Hawaii. Three weeks later she was back in the water and later returned to competitive surfing and other sports with her one good arm. She was fitted with an artificial arm made of graphite and silicon.

Body Levers Devices such as prosthetic arms are

possible because the human skeleton can be thought of as a system of bony levers. In the body, levers of bone are activated by muscles that produce movement. These principles of biomechanics are applied to the design of prosthetic arms and legs.

Figure 1 illustrates the arm as a third-class lever that has the fulcrum at the elbow, the force at the lower muscle connection, and the load in the hand. When the muscle pulls upward on the bone, the arm moves at the elbow, and the hand lifts the load.

LESSON 3

Bicep muscle

Elbowpivot

Softdrink

Figure 1

Prosthesis Types One type of prosthesis, the myoelectric

arm, uses small electric motors to move the replaced limb. When a muscle in the body contracts, or flexes, a small electric signal is created in the body and sent to a controller that switches the motors in the hand, wrist, and elbow on or off to produce movement and function. Disadvantages of this type of prosthesis are the inconvenience of a battery and severe damage to the motors and controller from water exposure.

Developed in 2008, a next generation prosthetic arm is called the Luke arm. This device attaches to nerves and decodes the signals that tell an arm, wrist, hand, and fingers what to do. When a person uses the Luke arm with an interface, he or she merely thinks about taking a drink of water, and sensors pick up and interpret electric impulses that tell the arm to perform the necessary actions. Figure 2 shows a prototype of the Luke arm.

A

B

C

D

Figure 2

Luke armprosthesis

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Challenge

Simple Machines and Your Day We use simple machines every day—levers, wedges, pulleys, inclined planes, screws, and

wheels and axles. Look around and see where they are. Some simple machines are easy to identify, but some might surprise you.

Observe and Describe Simple Machines Throughout a day at home or in school, identify five simple machines that you use.

Now choose one machine and draw a diagram of that machine in use. Describe how the machine operates. Indicate whether it is a lever, wedge, pulley, inclined plane, screw, or wheel and axle.

LESSON 3

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Lab A 40 minutes

Comparing Two Simple MachinesYou will use a pulley and an inclined plane to lift a 250-g mass to a height of 20 cm. Which simple machine makes the work of lifting the load the easiest?

QuestionWill the pulley or the inclined plane have a greater mechanical advantage?

Materials 250-g hanging mass 5-N spring scale small pulley

ring stand meterstick

Also needed: 50-cm × 15-cm board, books, 2-m length of heavy string

Safety


2. Examine the equipment and diagrams.

With your group, discuss why each simple machine has a mechanical advantage when lifting the mass.

3. Predict whether the pulley or the inclined plane will provide the greatest mechanical advantage in lifting the mass. Record your prediction.

4. What data will you need to collect to calculate mechanical advantage?

Use the data table. Add labels for the data you plan to collect to calculate mechanical advantage for each type of the simple machine.

Pulley Inclined Plane

Weight: Length:

Force: Height:

: :

: :

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Lab A continued

5. Use the spring scale to measure the weight of the 250-g mass.

Record the weight in newtons.

6. Set up the pulley and the ring stand as shown in your textbook. Adjust the spring scale and the pulley so that the weight just clears the table.

Use the spring scale to slowly lift the weight to a height of 20 cm on the meterstick.

Record the force in newtons in your data table.

Repeat.

7. Set up the inclined plane as shown in your textbook so the top of the ramp is 20 cm above the table.

Attach the spring scale to the weight.

Beginning at the bottom of the ramp, use the spring scale to pull the weight steadily up the ramp.

Record the force in newtons in your data table.

Repeat.

Lab Tips • A moveable pulley supports part of the weight, allowing less force to be used to lift the

object.

• The ideal mechanical advantage of an inclined plane is the length of the ramp divided by the height of the ramp.

Analyze and Conclude

8. Interpret Data What is the mechanical advantage of the pulley and the inclined plane? Was your hypothesis correct? Explain.



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Lab A continued

9. Explain What other measurements would you need in order to calculate the efficiency of each machine?

10. The Big Idea Did the amount of work done on the weight to lift it to a height of 20 cm change with each machine? Explain. Did the machines make doing the work easier?

Communicate Your ResultsMake a large data table on which all groups can display their data. Discuss similarities and differences between group data.

Remember to use scientificmethods.

Ask a Question

Form a Hypothesis

Test your Hypothesis


Communicate Results

Make Observations



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Lab B 40 minutes

Comparing Two Simple MachinesYou will use a pulley and an inclined plane to lift a 250-g mass to a height of 20 cm. Which simple machine makes the work of lifting the load the easiest?

QuestionWill the pulley or the inclined plane have a greater mechanical advantage?

Materials 250-g hanging mass 5-N spring scale small pulley

ring stand meterstick

Also needed: 50-cm × 15-cm board, books, 2-m length of heavy string

Safety


2. Examine the equipment and diagrams. With your group, discuss why each simple machine has a mechanical advantage when lifting the mass.

3. Predict whether the pulley or the inclined plane will provide the greatest mechanical advantage in lifting the mass. Record your prediction.

4. Make a data table with rows for the data you plan to collect to calculate mechanical advantage for each type of the simple machine.



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Lab B continued

5. Use the spring scale to measure the weight of the 250-g mass. Record the weight in newtons.

6. Set up the pulley and the ring stand as shown in your textbook. Adjust the spring scale and the pulley so that the weight just clears the table. Use the spring scale to slowly lift the weight to a height of 20 cm. Record the force in newtons. Repeat.

7. Set up the inclined plane as shown in your textbook so that the top of the ramp is 20 cm above the table. Attach the spring scale to the weight. Beginning at the bottom of the ramp, use the spring scale to pull the weight steadily up the ramp. Record the force in newtons. Repeat.

Lab Tips • A moveable pulley supports part of the weight, allowing less force to be used to lift the

object.

• The ideal mechanical advantage of an inclined plane is the length of the ramp divided by the height of the ramp.

Analyze and Conclude 8. Interpret Data What is the mechanical advantage of the pulley and the inclined plane?

Was your hypothesis correct? Explain.



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Lab B continued

9. Explain What other measurements would you need in order to calculate the efficiency of each machine?

10. The Big Idea Did the amount of work done on the weight to lift it to a height of 20 cm change with each machine? Explain. Did the machines make doing the work easier?

Communicate Your ResultsMake a large data table on which all groups can display their data. Discuss similarities and differences between group data.

Extension

How can you increase the mechanical advantage of your inclined plane? To investigate your question, design a controlled experiment.

Remember to use scientific methods.

Ask a Question

Form a Hypothesis

Test your Hypothesis


Communicate Results

Make Observations



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Lab C

Increasing Mechanical AdvantageDirections: Use the information and data from the Lab B Comparing Two Simple Machines to perform this lab.

In Lab B, you used a pulley and an inclined plane to lift a 250-g mass to a height of 20 cm. You discovered, through your experiment, which simple machine makes the work of lifting the load the easier. Now, use what you know to increase the mechanical advantage of your inclined plane.

Please note that you must complete Lab B before beginning Lab C. Also, have your teacher approve your design and safety procedures before beginning your experiment.



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Chapter Key Concepts Builder

Work and Simple Machines End-of-Chapter PracticeDirections: Answer each question on the lines provided.

1. When a force is applied to an object, what must occur for work to be accomplished on the object?

2. What is the unit of power, and what is the equation for calculating power?

3. How does a machine convert input work to output work?

4. What is a machine’s mechanical advantage, and how is it calculated?

5. Why is the efficiency of a machine always less than 100 percent?

Directions: Work with a partner. Select one of the options. When you have finished, present your results to the class.

6. Choose a simple machine and at least ten real-world applications of it. Locate a photograph or illustration of each use and create a pictorial presentation with captions.

7. Learn how a block-and-tackle pulley system works. Determine a few ways that this compound machine has been used throughout history. Locate photos and illustrations of the applications that you include and write captions to go with them.

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