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Work and Machines PacketBook M Chapter 3 (pages M 106- M 143)

Key Terms - write out the definitions for the following terms.

1. work

2. joule

3. power

4. machine

5. mechanical advantage

6. efficiency

7. inclined plane

8. wedge

9. screw

10. lever

11. fulcrum

12. wheel and axle

13. pulley

14. compound machine

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Work and Machines Guided Reading and Study

What Is Work?This ::.ectiOl1l!Xplllills the SCit'i'ltific l71ellIJillt: o.fwork and de::,crilies hot» to cuiculotethe ioork done on an object, The sectiollll/S0 exp!f7ili; IWiU~hnver i:::. cctculated.

Use Target Reading SkillsBefore you read the section, preview the red headings. In the graphicorganizer, ask a what or how question for each heading. As you read the textunder the heading, find the answer to your question. and record it in thegraphic organizer.

The Meaning of Work1. In scientific terms, when do you do work>

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Work and Machines Guided Reading and Study

What is Work? (continued)

2. Complete the following table by classifying each example as either workor no work.

tr

Work?

Example Work or No Work?

You pull your books out of your book bag.

You lift a bin of newspapers.

You push on a car stuck in the snow.

You hold a heavy piece of wood in place.

You pull a sled through the snow.

You hold a bag of groceries.--

3. In order for you to do work on an object, the object must move some___________ as a result of your force.

4. Explain why you don't do any work when you carry an object at aconstant velocity. 'i

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5. When you pull a suitcase with wheels, why does only part of your forcedo work?

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242

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Work and Machines Guided Reading and Study

• Calculating Work

6. The amount of work you do depends on 'both the amount of___________ you exert and the_____________ the object moves.

7. [s the following sentence true or false? Lifting a heavier object demandsgreater force than lifting a lighter object. ------------

8. What formula do you use to determine the amount of work done on an

object?

9. What is the Sl unit of work?10. What is the amount of work you do when you exert a force of 1newton

to move an object a distance of 1meter> ------------

power11. What is power>

!J 12. ls the following sentence true or false? You exert more power when yourun lip a flight of stairs than when you walk up the stairs.

13. What is the formula you use to calculate power>

14. Rewrite the equation for power in a way that shows what work equals.

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Work and Machines • Review and Reinforce

What Is Work? 6Understanding Main Idea,S •Use the following illustration to answer quesiions 1 through 3.

~F = 40 N

1. The illustration shows Beatrice pushing on a heavy box. Beatrice pusheswith a force of 40N. How can you determine if Beatrice is doing workon the box?

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"·-t2. Beatrice pushes the box 2 m to the right. What formula should you use

to calculate the amount of work done on the box?.r

I,!!)P"Vii3. How much work does Beatrice do pushing the box 2 m?

Building VocabularyWrite a definition for each of the following terms on the lines beloto.

4. work

5. joule

6. power...t

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Work and Power

Definition: Work = Force x distance

W = 125 lbs x 10 feet = 1250 foot-pounds

In International System (SI):Work = newton x metersWork = joule, or 1Nxl m

10 feet

In International System (81):Power = newton x meters (joules)

secondsPower = watt (1joule per second)

Definition: Power =Worktime

Power = 500 pounds x 60 feet = 6000 foot-pounds per second5 seconds

1. Find the work done in these situations.a. 50 kg moved 5m _

b. 100 N moved 10 m _

c. 25 kg carried 75 m _

125 pounds

5 seconds

60 feet

500 pounds

d. 10 N carried 125 m _

e. 1200 kg lifted 250 m _

f. 27 N lifted 3 m _

2. Find the amount of power used in these situations.a. 3000 foot-pounds of work done in 5 seconds _

b. 10,000 joules of work done in 10 seconds _

c. 150 kg of books moved 25 m in 50 seconds ~-------------3. Write the word from Column B in the space before its description in Column A.

Column A Column B

a. 1Newton x 1meter

h. Force x distance

c. 1 joule per second

d. ratio of work to time

e. effort or resistance

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watt

joule

force

work

power

9a Machines and Work

The Lever

effort

resistance

hammerand nail 1. crowbar 1. nutcracker

. shovel

3.

2.

1. lever

scissors

,. What are the three elements of a lever? _••...By each number above, write F for fulcrum., R for resistance, or E for effort.

definitions for each of the following:resistance _

the word or words that will make each sentence a true statement.________ have two connected levers that can be used to _paper or cloth.A _ is a simple machine that uses two hands as the _and _ of a lever to move dirt.

In second-class levers, the is between the effort and _

When the fulcrum is closer to the effort than to the resistance, there is a loss in

---- but a in speed and distance.

A seesaw is a common example of a, -class lever.

3a Machines and Work

Types of Levers,

R ~

E F

first-class lever second-class lever tbUrd-classlever

bottleopener

wheelbarrow

broom

1. In which type of lever are the resistance and effort moving in opposite directions? _

2. In which type of lever is the effort between the fulcrum and the resistance? _

3. Identify these machines as first, second, or third-class levers by writing 1, 2, or 3 in thespaces provided.a. crowbar e. pliers i. snow shovel

h. bottle opener f. broom j. seesaw

c. rowboat oars g. wheelbarrow k. nutcracker

d. fishing pole h. lifting weight 1. skull pivotingwith forearm on vertebra

4. Why is the position of the fulcrum important, particularly in first-class levers?

5. Why are pliers considered a first-class lever? _

©Milliken Publishing Company 3b ~aChines and Work

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The Wheel and Axle

The wheel and axle is a wheel connected to a rigid pole.

axle

lever

conveyor

log rollers A handle can be thought ofas a section of a wheel.

doorknob

Why does using a wheel and axle make work easier? _

How did early people make a wheel and axle for their carts? _

A conveyor belt, used to load or unload a truck, is made of which two simple machines?

The handle of a pencil sharpener is like the of a _

Milliken Publishing Company 4a M)l.Y Machines and Work

The Inclined Plane, Wedge, and ScrewThe wedge is an inclined planethat tapers to a sharp edge.

how the inclined plane in the top illustration assists the person moving the barrel.

are two inclined planes you have seen or used? _

ext to the wedges named, write whether they are used to split, cut, or fasten.d. spike _

e. hatchet _

f. doorstop _te the word or words that Willmake each sentence a true statement .

....Using an inclined plane to lift a barrel requires less over a greater

r,Using an inclined plane requiresbess effort over a longer distance.

without inclined plane

~/

~with inclined plane

inclined plane________1<=:::::::::::::e=:=:==:::::J

Single~

double wedge

:The screw is an inclined plane wound arourid a central cylinder.

over a --'-__ distance.Lifting the barrel from the ground to a platform requires effort

---- is an inclined plane wound around a cylinder ..arne two examples of screws other than the ones shown above. ----------------

5a (]) Machines and Work

The pulley movesalong the rope.

III.

about100 kgeffort

200 kg

1m.1. Label the types of pulleys inboxes I through III above.2. Label the fulcrum, resistance, and effort on lines A through C.3. Write the word or words that will make each sentence a true statement.

a. Three parts of a pulley are the grooved , the _and the rope.

h. A fixedpulley is like a turning -class lever because the

________ is between the and the resistance.

c. A movable pulley is like a turning -class lever because the

_________ is between the fulcrum and the _

d. The pulley is used primarily to change the direction offorce.4. Name the kind of pulley used for the following.

a. raising sails on a boat _

b. windowblinds _c. lifting very heavy weights _

d. painter's scaffold _

5. What prevents the rope from slipping off the wheel of a pulley? _

6. What is the function of a movable pulley? _

© Milliken Publishing Company 6a

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fCf"\J/ Machines andWork .f

The Block and TackleA block and tackle is a combination of fixed and movable pulleys.

For the single block and tackle above, write the fraction that tells how much effort is neededto lift the resistance: 112, 113, or 114.For the double block and tackle above, write the number of kilograms of effort needed to liftthe motor.Write the word or words that will make each sentence a true statement.

a. A block and tackle is also known as a pulley.

The two kinds of pulleys that make up a block and tackle are and

pulleys.c. A block and tackle changes the and increases _

d. The more strands of rope or wire required by a block and tackle, the greater the amount

of generated.

e. In practice, nothing is gained by more than _

6b

single blockand tackle

resistance:90 kg

double blockand tackle

fixed pulley:changes thedirectionafforce effort needed =

113 the resistanceeffort needed:about kg

movable pulley:changes theamountafforce

effort needed =the resistance-----

effort needed:about 45 kg

motor weight:270 kg

pulleys.

Machines and Work

A. _

D. __

Simple Machlnes·

B. c. _

rl F.

iE. _

1. Label the simple machines on lines A-F above.2. On the second line give an example of the machine other than the one pictured.3. Identify the following simple machines.

a. sloping surface _

h. rope over a wheel _

c. bar pivoting on a fixed point _

d. spiral inclined plane _

e. wheel connected to a shaft _

4. Narne the simple machine used to do the following.

f. slope tapering to a sharp edge _

d. fasten pieces of wood _a. chop wood _

b. load railroad cars _ e. reduce friction on rolling objects _

c. remove tacks _ f. raise and lower a sail _

5. Write the word or words that will make each sentence a true statement.

a. A machine can never do more work than the amount of put into it.

b. No matter how complex machines seem, they are all forms of six -------------machines.c. Simple machines help us make better use of our _

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Machines and Work

Compound MJlC!hines~-,.. :"L,;"_

wheelbarrowC. __

A. __ B. ~-

typewriter

pencil sharpener

E. _ hand drill

F. _

1. On the lines by each picture, write two of the simple machines found in each compoundmachine.

2. List two simple machines found in each of these compound machines.a. garden hoe: _

b. movie projector: _

c. automobile: _

d. alarm clock: _

3. A combination of or more machines m@kup a compound machine.

© Milliken Publishing Company 7a MaChin} ~ Work

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