Work And Simple Machines - Science Classroom 608

Date1LaboratoryActivityClassCalculating Work and PowerWhen work is done on an object, energy is transferred to the object. When a force acts on anobject and moves that object a certain distance, work is done on the object. Work (W ) is definedby the following equation.W F dIn this equation, F represents a force acting on the object and d represents the distance throughwhich the object moves as that force acts on it. In the metric system, force is measured in newtons(N), and distance is measured in meters (m). If a force of 1 newton acts on an object and theobject moves 1 meter while the force is acting on it, the value of F d equals 1 newton-meter(N-m), which is the same as to 1 joule (J) of energy being transferred.Power (P) is the rate at which work is done. It can be calculated by the following equation.P W/tIn this equation, W represents the work done and t represents the amount of time required todo the work. In the metric system, the unit of power is the watt (W). If 1 joule of work is done in1 second, W/t has a value of 1 J/s, which is equal to 1 watt.StrategyYou will determine the amount of work required to lift an object.You will determine the power used while lifting the object.Copyright Glencoe/McGraw-Hill, a division of the McGraw-Hill Companies, Inc.Materialsspring scalemass (1-kg)scissorsstringdowel (wood, about 50 cm long)masking tapeProcedurewire tie (plastic-coated)meterstickstopwatchFigure 11. Weigh the 1-kg mass using the metricspring scale. Record this value in the Dataand Observations section.2. Cut a 1.3-m length of string. Tightly tieone end of the string to the center of thewood dowel. Secure the knot with a pieceof masking tape to prevent the string fromslipping.3. Make a small loop at the other end of thestring and knot it. Attach the 1-kg mass tothe loop with a plastic-coated wire tie.4. Measure a 1-m distance along the stringfrom the dowel using the meterstick. Markthis distance on the string with a smallstrip of masking tape.5. Hold the dowel at both ends as shown inFigure 1.Work and Simple Machines9Hands-On ActivitiesName

NameDateClassLaboratory Activity 1 (continued)9.10.Figure 2Tape11.12.13.Have your lab partner use a stopwatch tomeasure the time required for the piece ofmasking tape on the string to reach thedowel. Record this value under Student 1in Table 1.Reverse roles with your lab partner andallow him or her to repeat steps 6–8.Record the time value under Student 2in Table 1.The size of the force that was needed toraise the 1-kg mass is equal to the weightof 1 kg. The distance that the 1-kg masswas raised is the distance between thedowel and the piece of masking tape,which is 1 m. Record the values for theforce and distance under Student 1 andStudent 2 in Table 1.Calculate the work you did to raise the1-kg mass and record this value underStudent 1 in Table 2.Calculate the power you developed liftingthe 1-kg mass. Record the value underStudent 1 in Table 2.Complete Table 2 using your lab partner’sdata from Table 1.Data and ObservationsWeight of 1-kg mass:Table 1Measurementtimeforce (N)distance10 Work and Simple MachinesStudent 1Student 2Copyright Glencoe/McGraw-Hill, a division of the McGraw-Hill Companies, Inc.Hands-On Activities6. Raise the 1-kg mass by winding up thestring on the dowel as shown in Figure 2.Keep the winding motion steady so thatthe string winds up and the mass rises at aconstant speed. Practice raising the massin this manner several times.7. You are now ready to have your lab partner measure the time it takes for you toraise the mass a distance of 1 m.8. Suspend the 1-kg mass from the dowel asbefore. At a signal from your lab partner,begin to raise the mass at a constant speedby winding the string on the dowel.

NameDateClassHands-On ActivitiesLaboratory Activity 1 (continued)Table 2CalculationStudent 1Student 2work (J)power (W)Questions and Conclusions1. Compare the amounts of work that you and your lab partner did.2. Why would you expect both amounts of work to be the same?3. Compare the amounts of power developed by you and your lab partner.Copyright Glencoe/McGraw-Hill, a division of the McGraw-Hill Companies, Inc.4. Why would you expect the amounts of power to differ?5. How do the amounts of work and power depend on the speed at which the 1-kg mass is lifted?Strategy CheckCan you determine the amount of work required to lift an object?Can you determine the power used while lifting an object?Work and Simple Machines11

NameDateThe BicycleHands-On Activities2LaboratoryActivityClassYou have learned about many simple machines that are used in compoundmachines. The bicycle is a familiar compound machine that uses a wheel and axle.James Starley designed and manufactured one of the first successful bicycles in1868. He developed his design so that once it was moving, only a small amount offorce would be required to keep the vehicle and driver in motion on level ground.A multigear bicycle can either multiply its speed or increase the force on thewheels. However, it can never do both at the same time. If the bicycle’s gearsincrease the force on the wheels, then the pedals turn at a faster rate than thewheels do. If the gears decrease the force on the wheels, the wheels turn fasterthan the pedals. The mechanical advantage of a bicycle is the number of timesthe force applied by the rider’s legs is multiplied. The speed advantage is thenumber of times the wheel turns for each rotation of the pedals. As themechanical advantage increases, the speed advantage decreases.StrategyYou will determine the mechanical advantage and the speed advantage of a multigear bicycle.You will explain the relationship between mechanical advantage and speed advantage.You will describe the distance traveled by a bicycle depending on the gear combination used.MaterialsCopyright Glencoe/McGraw-Hill, a division of the McGraw-Hill Companies, Inc.30-cm-long block of woodmultigear bicyclemeterstickProcedure1. Place a block of wood under the bottombracket of the bicycle’s frame so the rearwheel is lifted off the ground. Have yourlab partner steady the bicycle by holdingthe handle bars and the seat as shown inFigure 1.2. WARNING: Avoid placing your hand or anyobject near the rear wheel, chain, or gears.Rotate the pedals with one of your handsto make the rear wheel turn. Shift the gearsand observe the speed of the rear wheel asyou shift through each gear. Be sure tocontinue rotating the pedal as you switchgears. Switching gears without moving thepedal may result in the chain jumping offthe gears. Record your observations in theData and Observations section.3. Remove the bicycle from the block of woodand lay it on its side. Count the number ofteeth in each gear of both the front sectionand rear section. Record the data in Table 1.Figure 1Work and Simple Machines13

NameDateClassRear gearsFront gears4. Measure the diameter of the bicycle’s rearwheel to the nearest centimeter. Record thisin the Data and Observations section.5. Set the bicycle upright. Place the gears inthe lowest gear combination, with the chainon the smallest sprocket of the front gearsand the largest sprocket of the back gears.6. Measure how many centimeters the bicycletravels as the pedal makes one completerevolution. Mark the starting and endingpoints using the front edge of the front tireand measure the distance between thesetwo points. Record this distance in theExperimental column in the data table.7. Repeat steps 5 and 6 for each of theother gear combinations. Record yourobservations.8. Calculate the mechanical advantage(M.A.) for each gear combination usingthe equation below. Record your answers.number of teeth on rear gearM.A. number of teeth on front gear9. Calculate the speed advantage (S.A.) foreach gear combination using the equationbelow. Record your answers.number of teeth on front gearS.A. number of teeth on rear gear10. Find the theoretical distance the bicycleshould travel as the pedal makes onerevolution for each gear combinationusing the equation below. Record youranswers. (π 3.14)Distance S.A. rear wheel diameter π11. Calculate the experimental error betweenthe theoretical and the experimentaldistance traveled using the equationbelow. Record your answers.Percent error theoretical – experimental 100%theoretical12. Graph the mechanical advantage versusthe speed advantage on graph 1.Graph 1Data and Observations1. Effect shifting gears has on the rear wheelspeed:542. Bicycle’s rear wheel diameter:Speed advantageHands-On ActivitiesFigure 2321000.20.40.60.8Mechanical advantage14 Work and Simple Machines1.01.2Copyright Glencoe/McGraw-Hill, a division of the McGraw-Hill Companies, Inc.Laboratory Activity 2 (continued)

NameDateClassHands-On ActivitiesLaboratory Activity 2 (continued)Table 1FrontteethRearteethM.A.S.A.Experimentaldistance (cm)Theoreticaldistance (cm)PercenterrorQuestions and ConclusionsCopyright Glencoe/McGraw-Hill, a division of the McGraw-Hill Companies, Inc.1. Why is a high mechanical advantage important to bicycle riders?2. Why is a high speed advantage important to bicycle riders?3. What simple machines are involved in a bicycle?4. What is the mathematical relationship between mechanical advantage and speed advantage?Work and Simple Machines15

NameDateClassLaboratory Activity 2 (continued)6. Which gear combination produced the greatest speed advantage in the bicycle you tested?7. Under what conditions is friction useful in riding a bicycle?8. How does friction make riding a bicycle more difficult?Strategy CheckCan you determine the mechanical advantage and the speed advantage of a multigearbicycle?Can you explain the relationship between mechanical advantage and speed advantage?Can you describe the distance traveled by a bicycle depending on the gear combination used?16 Work and Simple MachinesCopyright Glencoe/McGraw-Hill, a division of the McGraw-Hill Companies, Inc.Hands-On Activities5. Which gear combination produced the greatest mechanical advantage in the bicycle you tested?

NameDateClassHands-On ActivitiesWork and Simple MachinesDirections: Use this page to label your Foldable at the beginning of the chapter.WorkInclined PlaneLeverWheel and AxlePulleyCopyright Glencoe/McGraw-Hill, a division of the McGraw-Hill Companies, Inc.Work is done when a force causes an object to move.2 circular objects of differentsizes attached to rotate together2 types include screwsand wedgesa grooved wheel with a ropeor chain wrapped around itany rod that rotates orpivots about a fulcrumWork and Simple Machines17

Meeting Individual NeedsMeeting IndividualNeeds18 Work and Simple Machines

NameDateDirected Reading forContent MasteryClassOverviewWork and Simple MachinesDirections: Use the following terms to complete the concept map below.pulleysinclined planeswheels and axlesscrewsleverswedgesMeeting Individual NeedsSimple machinesincludeinclinedplane types4.5.6.such as1.Copyright Glencoe/McGraw-Hill, a division of the McGraw-Hill Companies, Inc.and2.and3.Directions: In the spaces provided, write the letters of the words or phrases that best answer the questions.7. Why are machines useful?a. They can increase force.b. They can increase distance over which force acts.c. They can change direction of force.d. all of these8. If you are standing still and holding a heavy iron doorstop in front ofthe class to demonstrate a wedge, are you doing work?a. yesb. noc. maybed. all of theseWork and Simple Machines19

NameDateDirected Reading forContent MasterySection 1Class Work and PowerDirections: Write work on the line provided if work is done, and none if no work is done.1. Someone is sitting on a cushion on the floor.2. The cushion is picked up and put on the couch.3. The cushion is put back on the floor.4. A baseball is hit into the bleachers.6. You study two hours for a science test.7. A little girl on a swing is pushed by her father.Directions: Draw lines matching the units of measure in Column I with the words in Column II as used in theformula below.Column I8. watt (W)9. newton (N)10. joule (J)11. meter (m)12. second (s)Column IIa. timeb. distancec. workd. forcee. powerDirections: Use the formulas to solve the following problems.work force distancework donepower time needed13. a. How much work was done to move a 10 N book 5 meters?b. What power was used if it took 2 s?14. a. Two people each applied 100 N of force to move a crate 3 m. How muchwork was done?b. How much power was used if it took them 60 s?20 Work and Simple MachinesCopyright Glencoe/McGraw-Hill, a division of the McGraw-Hill Companies, Inc.Meeting Individual Needs5. You lift your arms over your head.

NameDateDirected Reading forContent MasterySection 2Section 3Class Using MachinesSimple MachinesDirections: Use the following terms to label each simple machine.pulleyscrewwedgewheels and axleMeeting Individual Needsleverinclined planeCopyright Glencoe/McGraw-Hill, a division of the McGraw-Hill Companies, Inc.Directions: Circle the term that correctly completes each sentence.7. Mechanical advantage is the number of times the input force is(divided/multiplied) by a machine.8. The point about which a lever pivots is called a (fulcrum/rotator).9. Wedges and screws are both (levers/inclined planes).10. An inclined plane allows you to lift a heavy load by using (less/more) force overa greater distance.11. One way to reduce friction and increase efficiency is to add (input/lubricant).12. A wheel and axle consists of two circular objects of (different/identical) sizesthat are attached in such a way that they rotate together.13. When you use a machine, the output work can never be (greater/less) than theinput work.14. A fixed pulley changes the (distance/direction) of the force you exert.Work and Simple Machines21

NameDateDirected Reading forContent MasteryClassKey TermsWork and Simple MachinesDirections: Write the correct terms next to their definitions below.inclined planecompound machineefficiencypowerwedgeleveroutput forcemechanical advantagescrewwheel and axleinput forcesimple machineworkpulleyMeeting Individual Needs1. when a force produces motion in the direction of theforce2. the force you exert when using a machine3. the force you must overcome when using a machine4. a comparison of the input force applied to a machineto the output force it must overcome5. the ability of a machine to convert input work intooutput work7. machine made of two or more simple machines8. a flat, sloped surface9. an inclined plane that moves10. a machine with one movement11. an inclined plane wrapped around a cylinder12. two circular objects of different sizes that areattached in such a way that they rotate together13. any rigid rod or plank that pivots about a point14. a grooved wheel with a rope or chain wrappedaround it22 Work and Simple MachinesCopyright Glencoe/McGraw-Hill, a division of the McGraw-Hill Companies, Inc.6. the rate at which work is done

NombreFechaLectura dirigida paraDominio del contenidioClaseSinopsisTrabajo y máquinas simplesInstrucciones: Usa los siguientes términos para completar el mapa conceptual.poleasplanos inclinadospalancasruedas y ejestornilloscuñasSatisface las necesidades individualesLas máquinassimplesincluyentipos deplanos inclinadoscomo4.5.6.1.Copyright Glencoe/McGraw-Hill, a division of the McGraw-Hill Companies, Inc.y2.y3.Instrucciones: En los espacios dados, escribe la letra de las palabras o frases que mejor responden cada pregunta.7. ¿Por qué son útiles las máquinas?a. porque pueden aumentar la fuerzab. porque pueden aumentar la distanciac. porque pueden cambiar la dirección de una fuerzad. todas las anteriores8. ¿Realizas trabajo si te paras en un sitio y sostienes una tranca de puertapesada en frente de la clase para demostrar una cuña?a. síb. noc. tal vezd. todas las anterioresTrabajo y máquinas simples23

NombreFechaLectura dirigida paraSección 1Clase Trabajo y potenciaDominio del contenidioInstrucciones: En los espacios asignados, escribe trabajo si se hace trabajo y ninguno si no se hace trabajo.1. Alguien está sentado en el suelo sobre un cojín.2. El cojín es levantado y puesto sobre el sillón.4. Una pelota de béisbol es lanzada a la gradería.5. Levantas tus brazos por encima de tu cabeza.6. Estudias dos horas para tu examen de ciencias.7. Una niña en el columpio es empujada por su padre.Instrucciones: Une con una línea cada unidad de medición de la Columna I con las palabras de la Columna IIque se usan en la fórmula que aparece más abajo.Columna I8. vatio9. newton (N)10. julio (J)11. metro (m)12. segundo (s)Columna IIa. tiempob. distanciac. trabajod. fuerzae. potenciaInstrucciones: Usa las fórmulas para resolver los problemas siguientes.trabajo realizadopotencia trabajo fuerza x distanciatiempo requerido11. a. ¿Cuánto trabajo se hizo para mover un libro de 10 N 5 metros?b. ¿Qué potencia se usó si tomó 2 s?12. a. Dos personas aplicaron 100 N de fuerza cada una para mover una caja 3 m.¿Cuánto trabajo se hizo?b. ¿Cuánta potencia se usó si les tomó 6 s?24 Trabajo y máquinas simplesCopyright Glencoe/McGraw-Hill, a division of the McGraw-Hill Companies, Inc.Satisface las necesidades individuales3. El cojín es puesto de nuevo en el suelo.

NombreFechaLectura dirigida paraDominio del contenidioSección 2Sección 3Clase Usa máquinasMáquinas simplesInstrucciones: Usa los términos para rotular cada máquina simple.poleatornillocuñarueda y ejeSatisface las necesidades individualespalancaplano inclinadoInstrucciones: Encierra en un círculo el término que completa correctamente cada oración.Copyright Glencoe/McGraw-Hill, a division of the McGraw-Hill Companies, Inc.7. La ventaja mecánica es el número de veces que la fuerza de entrada es (dividida/multiplicada) por la máquina.8. El punto en el cual una palanca rota se llama (fulcro/rotador).9. Las cuñas y tornillos son (palancas/planos inclinados).10. Un plano inclinado permite que levantes una carga pesada usando (menos/más)fuerza a lo largo de una distancia mayor.11. Una manera de reducir la fricción y aumentar la eficiencia es agregando(entrada/lubricantes).12. Una rueda y eje consiste de dos objetos circulares de (idéntico/diferente)tamaño que están unidos de tal forma que rotan juntos.13. Cuando usas una máquina, el trabajo de salida nunca puede ser (másgrande/menor) que el trabajo de entrada.14. Una polea fija cambia la (distancia/dirección) de la fuerza que haces.Trabajo y máquinas simples25

NombreFechaClaseLectura dirigida paraTérminos clavesDominio del contenidioTrabajo y máquinas simplesInstrucciones: Escribe los términos correctos al lado de sus definiciones.plano inclinadomáquina compuestaeficienciapotenciacuñapalancafuerza de entradaventaja mecánicatornillorueda y ejefuerza de entradamáquina simpletrabajopoleaSatisface las necesidades individuales1. cuando una fuerza produce movimiento paralelo a ladirección de la fuerza2. la fuerza que haces cuando usas una máquina3. la fuerza que debes superar cuando usas unamáquina4. comparación entre la fuerza de entrada que se aplicaa una máquina y la fuerza de salida que debe superar6. tasa a la cual se hace el trabajo7. máquina hecha de dos o más máquinas simples8. superficie plana en declive9. plano inclinado que se mueve10. máquina con sólo un movimiento11. Plano inclinado enrollado alrededor de un cilindro12. dos objetos circulares de tamaño diferentes que estánunidos de tal forma que rotan juntos13. barra

Work and Simple Machines 3 Name Date Class Work and Power Analysis Calculate and compare the work and power in each case. Procedure Hands-On Activities 1. Weigh yourself on a scale. 2. Multiply your weight in pounds by 4.45 to convert your weight to newtons. Record your data in the Data and Observations section. 3. Measure the vertical height .