UTeach Outreach The University of Texas at AustinForces and Motion – Scripted VersionLesson created by: UTeach OutreachLength of lesson: 50-70 minutesTeacher Note: to make fit into a 50-minute class you can remove the history taught in thelesson and make the Elaboration a class demonstration.Description of the class: 6thand 8thGrade ScienceTEKS and NSES addressed:§112.20. Science, Grade 6, Beginning with School Year 2010-2011.(3) Scientific investigation and reasoning. The student uses critical thinking, scientific reasoning, andproblem solving to make informed decisions and knows the contributions of relevant scientists. Thestudent is expected to:(D) relate the impact of research on scientific thought and society, including the history ofscience and contributions of scientists as related to the content.(8) Force, motion, and energy. The student knows force and motion are related to potential andkinetic energy. The student is expected to:(B) identify and describe the changes in position, direction, and speed of an object whenacted upon by unbalanced forces;§112.20. Science, Grade 8, Beginning with School Year 2010-2011.(3) Scientific investigation and reasoning. The student uses critical thinking, scientific reasoning, andproblem solving to make informed decisions and knows the contributions of relevant scientists. Thestudent is expected to:(D) relate the impact of research on scientific thought and society, including the history ofscience and contributions of scientists as related to the content.(6) Force, motion, and energy. The student knows that there is a relationship between force, motion,and energy. The student is expected to:(A) demonstrate and calculate how unbalanced forces change the speed or direction of anobjects motion;(C) investigate and describe applications of Newtons law of inertia, law of force andacceleration, and law of action-reaction such as in vehicle restraints, sports activities,amusement park rides, Earths tectonic activities, and rocket launches.NATIONAL SCIENCE EDUCATION STANDARDS (1996):Content Standard A (Grades 5-8)1
USE APPROPRIATE TOOLS AND TECHNIQUES TO GATHER, ANALYZE, AND INTERPRET DATA. The useof tools and techniques, including mathematics, will be guided by the question asked and theinvestigations students design. The use of computers for the collection, summary, and display ofevidence is part of this standard. Students should be able to access, gather, store, retrieve, andorganize data, using hardware and software designed for these purposes.UNDERSTANDINGS ABOUT SCIENTIFIC INQUIRY• Mathematics is important in all aspects of scientific inquiry.Content Standard B (Grades 5-8)• An object that is not being subjected to a force will continue to move at a constant speed andin a straight line.• If more than one force acts on an object along a straight line, then the forces will reinforce orcancel one another, depending on their direction and magnitude. Unbalanced forces will causechanges in the speed or direction of an objects motion.OverviewStudents are introduced to the effect of forces on the motion of objects. The students view videos offorces in action and identify the forces present. The contributions of Galileo Galilei and Sir IsaacNewton are briefly discussed and related to the motion of objects observed every day. The studentsobserve a demonstration of Newton’s first law of motion, then transition to the Forces and MotionBasics PhET computer simulation to investigate the effect of force on motion. The students observethe effect of friction on the motion of an object, as well as, the theoretical case without friction. Thestudents are also introduced to the relationship between an applied force and the acceleration of anobject. Students consider the advantages and disadvantages of using a computer simulation to modelthe motion of an object. To elaborate on the material, the students use blocks and a piece ofcardboard to model how buildings collapse during earthquakes. The October 23, 2011 earthquake inTurkey is discussed and students hypothesize how the movement of the earth can affect buildingstructures. A connection is made to careers in engineering.Objectives (learner outcomes)Students will be able to:• identify when an object is being acted upon by unbalanced forces.• predict the change in motion when a force is applied to an object.• demonstrate an understanding of how unbalanced forces relate to the total force applied toan object.• utilize Newton’s Law of Inertia (velocity remains constant unless acted upon by an unbalancedforce) to describe the motion of an object when acted upon by an unbalanced force.• identify the advantages and limitations of using the “Force and Motion” PhET simulation.2
• identify the contributions of Galileo Galilei and Isaac Newton to the study of motionResources, materials and supplies neededExperiment 1: per class (if using as a demo) or per pair of students• 1 plastic cup• 1 penny• 1 playing cardExplore: per pair of students• One computerElaborate: per pair of students• 30 blocks• Piece (12 inches x 12 inches) of cardboardSupplementary materials needed for each class and worksheets• See attached.• “Forces and Motion Turkey Earthquake” PowerPoint.Advanced PreparationEngage – Have the following video clips ready to play• Bow and Arrow: http://youtu.be/BWZ4WJQ-624• Triple Jump: http://youtu.be/zCvFz1oCNQ4• Motorcycle Coming to Stop: http://youtu.be/Mk7b2oWQPR0Explore• Practice penny flick (Experiment 1) a few times.• Have Forces and Motion Basics PhET simulation bookmarked on student computers.Elaborate• Have “Forces and Motion Turkey Earthquake” PowerPoint loaded or print out of slidesmade per group of four.Background InformationCollege Level:3
The motion of objects has long been a topic of study in physics, dating back as far as Aristotle (384 -322 BCE). Aristotles works on motion prompted the classification of effects acting on a movingobject. While the content of his principles has been relegated to historical studies, the analyticalprocess continues today. The motion of an object is analyzed by separating it into distinctcomponents, paying attention to properties which remain constant, or in other terms are"conserved." This simplifies the characterization of an objects motion - conserved quantities will notchange, so they are independent of circumstance. More modern kinematics, the study of motion,from Galileo and then Newton were derived from this analysis and the intermediate advancementsin mathematics.Replica Bust of Aristotle Portrait of Galileo Portrait of Newton(384 – 322 BCE) (1564 – 1642) (1643 – 1727)Photographs retrieved from the following web pages, respectively.http://en.wikipedia.org/wiki/File:Aristotle_Altemps_Inv8575.jpghttp://en.wikipedia.org/wiki/File:Justus_Sustermans_-_Portrait_of_Galileo_Galilei,_1636.jpghttp://en.wikipedia.org/wiki/File:GodfreyKneller-IsaacNewton-1689.jpgGalileo Galilei (1564 - 1642) is credited for arguing the constancy of velocity in the absence ofexternal forces. He treated friction as a force which opposed motion, causing a deceleration. Thus,on a frictionless, infinite surface, Galileo proposed that an object would maintain a constant velocityin a straight line forever, provided it experienced no external forces. Identifying friction as the causeof objects to slow to a stop revolutionized the philosophy of motion. Motion in a straight line withconstant speed became the standard behavior of objects rather than zero motion. Galileosexperiments with gravity quantified the acceleration of objects of equal size and different densities.Neglecting the force of the air, the acceleration experienced due to gravity is constant andindependent of mass. These two premises were further refined in Newtons research.4
The surface in the above picture is ice, which is approximated as frictionless.Galileo’s work on physics stated that an object will maintain a constantvelocity in the absence of external forces. Here, the wooden block haszero velocity, and without an external force it will never change.Image from Forces and Motion simulationThe modern equations of motion proposed by Sir Isaac Newton (1643 – 1727) in 1686 form the basisof classical mechanics, the body of knowledge still used to predict the behavior of physical systemstoday. For movement very slow compared to the speed of light (about 670 million miles per hour),these equations are an excellent approximation. Newton founded his model on three laws: first, anobject or group of objects will maintain a state of rest or state of constant linear motion unless actedupon by a net external force; second, a force is any action or reaction which causes an object withmass to accelerate, and the force is equal to the product of the mass and the acceleration; third, forevery action (force) acting on an object, there is an equal and opposite reaction (force) which isexerted back onto the body initiating the acceleration.Newtons first law builds on Galileos earlier work by noting that the total velocity of all objects in aclosed system is not necessarily conserved, but the total momentum is. A closed system means thatno energy is entering or leaving the system, so the system is isolated from external influences. Thisprovides a good representation of a collision of two or more objects that are not under the influenceof a force.Newton’s formulation of Galileo’s earlier work states thatmomentum is constant in the absence of external forces.Image from Forces and Motion simulationNewtons second law defines the force referenced in the second law. Earlier descriptions of force5
used various terms, so Newton had to specify that a Newtonian force is,Newtons third law states that any object which is pushed will react to being pushed. This reaction is aforce applied back on whatever object initiated the push. If you push on an object, you feel thesurface of the object. That sensation is due to the reaction force of the object resisting your push. Theobject resists your hand moving through the object just as much as your hand resists the objectmoving through your hand. The quantity, or magnitude, of force between any pair of objects is thesame whether you look at the action force or the reaction force. The net force is the vector sum of allthe forces acting upon an object. When the forces acting upon an object are in balance the net forceis zero. If the forces acting upon an object are unbalanced the net force is nonzero.Diagram showing force pairs according to Newton’s Third LawThe force of the table on the floor is equal to the force of the floor on the table.The force of the book on the table is equal to the force of the table on the book.Middle School Level:The way objects move and how their motion changes has been a topic of study in physics for a longtime. In addition to many other things, Galileo Galilei (1564 - 1642) studied how objects slow downwhen moving on a level surface. He realized that there must be a force causing it – friction. BeforeGalileo, friction was not treated like a force. In fact, friction as we know it was not a part of science atall. When he realized that friction was a force, Galileo figured out that if friction was not present, anobject would continue moving on a level surface forever at a constant rate. Since this rate is in factvelocity, this means that the velocity of the object would stay the same. The object’s motion would6
only change if it experienced a force.Since the box above rests on a frictionless surface, approximated by ice,and it has no net force applied to it, its velocity will remain constantuntil it experiences a net force.Image from Forces and Motion Basics simulationSir Isaac Newton (1643 – 1727) improved on Galileo’s study of motion and friction by finding out howmultiple objects interact with each other. Newton realized that the effect of gravity was a forcepulling all objects together. He published his findings and the mathematics he used to predict motionin 1686. In his book, Newton proposed that there are three laws of motion. His first law is that anobject or group of objects will remain in motion or stay at rest unless an external force is applied.Newton’s second law defines a force as anything that causes an object to change the way it moves, inother words, a push or a pull. The third law of motion is best explained by using two objects in anexample. If object A pushes on object B, object B resists the push. Object A experiences this resistanceas a push (force), and the amount of force from B to A is the same as the amount of force from A to B.However, the force (push) of A on B is in the opposite direction as the force of B on A.Amount of Force from B to A = Amount of Force from A to BThis diagram shows Newton’s third law of motion.Object A applies a force on object B, and object B resists.The resistance is a force of the same magnitude, but opposite direction.7vA B
Using these three laws and some additional mathematics, Newton was able to predict many differenttypes of motion. This was the start of our modern physics.Adding up the forces acting on an object gives the net or total amount of force acting on an object. Ifthe net force acting on an object is zero, then the forces acting on the object are in balance. If the netforce acting on an object is nonzero, then the forces acting on the object are unbalanced.VII. Possible Misconceptions• Students may have trouble with the concept that an object slowing down has anacceleration. The key idea is that acceleration is the slowing down (deceleration) andspeeding up (acceleration) of an object.• Students may not think of friction as being a force. Friction is responsible for the slowingdown of an object. It often is an unbalanced force that causes an object to come to a stop.• When the students flick the playing card in Experiment 1, they may believe that they onlyapply a force to the card and not the penny, so the penny stays still until the card moves outfrom underneath it. In reality, the net or total force on the penny changes when flicking theplaying card, both downward and sideways. Since there is not much friction between thepenny and playing card, only a small amount of the force applied to the playing card istransferred to the penny. Since the net sideways force changes, even though it is very small,the penny moves in that direction. But since the force is very small, it does not move much.When the force of gravity is no longer balanced by the playing card, the penny drops down.Because the force of gravity is much greater than the sideways force from flicking the card,the direction of motion is mainly downward.VIII. Vocabulary and DefinitionsCollege Level:•Force: an influence that causes an object to change direction or speed•Gravity: a phenomenon that causes two bodies to attract with a force proportional to their mass•Velocity: the rate of change of position of an object•Acceleration: the rate of change of the velocity of an object•Net force: the sum of all the forces acting on an objectMiddle School Level:•Force (fuerza): a push or a pull•Gravity (gravedad): a force that causes two objects to come together•Velocity (velocidad): how fast or slow an object is moving8
•Acceleration (aceleración): how much an object is speeding up or slowing down•Net force (fuerza neta): the sum of all the forces acting on an objectIX. Safety Considerations• When students flick card in Experiment 1, ask them to flick card away from others.X. Question of the Day• How can forces affect the motion of an object?9
FIVE-E ORGANIZATIONENGAGEMENT Time: 5 minutesWhat the Teacher Will Do Probing Questions Student ResponsesPotential MisconceptionsToday we’re going to start byviewing a few video clips. Payattention to the motion of thepeople in the video clips.Play video clips for students.Bow and Arrow:http://youtu.be/BWZ4WJQ-624Triple Jump:http://youtu.be/zCvFz1oCNQ4Motorcycle Coming to Stop:http://youtu.be/Mk7b2oWQPR0In the bow and arrow video, theman pulls back the bow and thearrow is shot. In the Triple Jump,the jumper sprinted as fast as hecan to jump a long distance. Themotorcyclist applies the brakes tomake the motorcycle come to astop.1. What did youobserve in eachvideo clip?2. What did the persondo in each clip?3. What did archerprovide when hepulled back the bow?1. Bow and arrow, longjumper landing,motorcycle comingto immediate stop(i.e. slam brakes)2. Person shootingarrow from bow,jumper sprinting fastand jumping as far ashe can into the pit ofsand, motorcycleengine moves it andbrakes help it cometo a halt.3. A force.10
ENGAGEMENT Time: 5 minutesWhat the Teacher Will Do Probing Questions Student ResponsesPotential MisconceptionsCorrect, a force was applied ineach video clip to cause a changein the motion of an object. Recall,a force is a push or pull, whichhas both magnitude (size) anddirection.Today we are going to beinvestigating our Question of theDay: “How can forces affect themotion of an object?”Post Question of the Day on theboard.4. When themotorcyclist stoppedhis motorcycle whatdid the brakesprovide?5. What did thejumper’s legsprovide?4. A force.5. A force.EXPLORATION Time: 30 minutesWhat the Teacher Will Do Probing Questions Student ResponsesPotential MisconceptionsOptional History Section (20minutes)To begin our lesson on forcesand motion, let’s brieflydiscuss some history. We haveobserved in class that allobjects fall at the same rate ifthere is little air resistance.Galileo Galilei was aphilosopher in the late 1500sand early 1600s thatdiscovered the idea that1. Where have you heardof Galileo before?1. He’s a scientist. He’sold. His study of theplanets.11
EXPLORATION Time: 30 minutesWhat the Teacher Will Do Probing Questions Student ResponsesPotential Misconceptionsobjects fall at the same ratewith little air resistance andfound that objects have aconstant acceleration due togravity on earth. Show imageof Galileo Gailei. However,scientists thought that ourgravity was something uniqueto earth.Some people that that ifobjects experienced gravitysomewhere else the gravitywould be different. Sir IsaacNewton, a philosopher in the1600s, developed an equationthat determined the force ofgravity everywhere in theuniverse. Show image of SirIsaac Newton. In order todescribe gravity, he realizedhe needed to describe whatforces are and how they relateto the motion of objects.Excellent! Those are all greatexamples of Newton’s Laws ofMotion.2. What do you think itwould mean if gravitywas unique to Earth?3. What Newton isfamous for?4. What are a few ofNewton’s Laws?2. It’s only on Earth.Somewhere else thereis a different gravity.3. Three laws of motionand talking aboutgravity.4. An object at rest staysat rest, for everyaction there is anequal and oppositereaction, etc.12
EXPLORATION Time: 30 minutesWhat the Teacher Will Do Probing Questions Student ResponsesPotential MisconceptionsI want everyone to pick up asmall object off your desk andstand up as we attempt torelease the object from ourhands. Ready ‘1…2…3’, releasethe object! Now, everyone pickup your objects and put themback on your table.The floor caused the object tocome to a stop (or rest);otherwise, Newton claimedthe objects would fall directlytowards the center of theearth.Thus, the ground must providean upward resistance to themotion of the object. In ourcase, the floor provided thisforce. After the object makescontact with the floor, theobject comes to a rest (orstop).Those are all great examples5. What force wasresponsible for pullingthe objects wedropped to theground?6. And what is gravity?7. Why didn’t the objectskeep on falling?8. What are a fewobjects around theroom that are at rest?5. Gravity.6. A force.7. The ground causedthe objects to come toa stop (or rest).8. Books on the table orthe tables themselves.13
EXPLORATION Time: 30 minutesWhat the Teacher Will Do Probing Questions Student ResponsesPotential Misconceptionsof objects that are at rest.Great answer! An object thatis still and not moving is atrest.Right! The forces arebalanced. When our objectshit the floor, the groundprovided an upward force,while gravity produces thedownward force. These forcesare in balance after the objecthits the floor because theobject has come to rest.We can add up the forces onan object. This can give us abetter idea of if the forcesacing on an object arebalanced or unbalanced.Forces in opposite directionshave opposite signs. We callthe sum of all the forces actingon an object the net force ortotal force. The net force tellsyou what the total force on anobject is.9. How would you defineat rest?10. When an object is atrest are the forcesbalanced orunbalanced? Why?11. If there are balancedforces on an object,what would we get ifwe added up all of theforces?9. Not moving.10. Balanced.11. Nothing, zero.14
EXPLORATION Time: 30 minutesWhat the Teacher Will Do Probing Questions Student ResponsesPotential MisconceptionsIf the sum of all the forces iszero, the forces are balanced.If the sum of all of the forces isnot zero, then the forces areunbalanced. Write this in yourscience journals.Give an example, if necessary.Today, we will experimentwith Newton’s first law invarious applications and thentest it in a computersimulation.End Optional History SectionExperiment 1:Do experiment either as ademonstration or have thestudents work in pairs.Pass out “Forces and MotionExperiment” Sheet.The first experiment we aregoing to look at will relate toNewton’s First Law of Motion.Here I have a penny on top ofa playing card resting on top12. If the net force is zero,are the forcesbalanced orunbalanced? Why?13. If the net force is notzero, what does thattell you? Why?12. Balanced. Because theforces are in oppositedirections.13. That the object maybe moving.15
EXPLORATION Time: 30 minutesWhat the Teacher Will Do Probing Questions Student ResponsesPotential Misconceptionsof a cup. I’m going to flick theplaying card and I want you tomake a few observations.Quickly flick the playing card.Let’s talk about the forcesacting on the penny. Answerthe four questions on yoursheet with your partner. Givestudents two minutes toanswer questions.14. What observations canyou make about thepenny resting on theplaying card?15. Are the forcesbalanced orunbalanced?16. What happened?17. When I flick theplaying card, what amI applying?18. When I apply a force,by flicking the playingcard, are the forcesacting on the playing14. It is stationary, notmoving.15. The forces are inbalance, becauseobjects are at rest.16. The penny fell in thecup! The playing cardwent flying!17. A force.18. Unbalanced. Becausethe playing cardmoves.16
EXPLORATION Time: 30 minutesWhat the Teacher Will Do Probing Questions Student ResponsesPotential MisconceptionsAlthough gravity was actingon both objects, gravity wasthe most significant forceacting on the penny. Theperson that flicked the playingcard provided another forcethat caused the playing cardto be moved out fromunderneath the penny. Keepin mind the person only flickedthe playing card not thepenny.Newton’s first law says that ancard balanced orunbalanced? Why?19. What force acted onthe penny?20. What is the net forceon the penny before Iflick the playing card?As it falls into the cup?21. In this experiment,what was at rest andwhen was it at rest?22. In this experiment,what was in motionand when was it inmotion?19. Gravity. The playingcard being flicked dida little bit.20. Zero. Nonzero.21. The penny before andafter the card wasflicked. The playingcard before and afterit was flicked.22. The playing card afterflicking it. The pennywhen it moveddownward.17
EXPLORATION Time: 30 minutesWhat the Teacher Will Do Probing Questions Student ResponsesPotential Misconceptionsobject in motion will remain inmotion until it’s acted upon bysome force and an object atrest will remain at rest unlessacted upon by an outsideforce.This short experiment relatesto Newton’s First Law ofMotion because an outsideforce did not act on the pennyso it remained at rest. Byflicking the playing card, aforce was applied to theplaying card so it moved.It is important to note that thepenny does move slightlyforward, but gravity is a moresignificant force and pulls thepenny into the cup.Today, we’re going to use acomputer simulation so wecan see all of the forces actingon an object. These forces willappear as arrows in thesimulation.Have computer simulationloaded on projector in frontof the class.Take the next five minutes toexplore the simulation.23. How does Newton’sFirst Law relate towhat we just sawwhen we flicked theplaying card?23. There was a forceapplied to the playingcard that caused it tomove forward whichwas provided by yourfinger. Once youflicked the card, itmoved out fromunder the penny andthe penny dropped tothe bottom of the cupdue to gravity.18
EXPLORATION Time: 30 minutesWhat the Teacher Will Do Probing Questions Student ResponsesPotential MisconceptionsPass out “Forces and MotionPhET Simulation” Worksheet.Give students a few minutesto push the crate back andforth and answer the keyterms on the top of theirsheet.After a few minutes, select acouple students to share whatthey have discovered and goover key terms, if needed.Make sure students mention:1. “Reset All” button2. How you can enter in aforce then press enter and thecrate will move3. How you can click and dragthe boxNow that we have anunderstanding of how thesimulation works, I want youto complete the rest of thesections in your “Forces andMotion PhET SimulationSheet.” Be sure to write incomplete sentences.Give students 30 minutes tocomplete all sections.Possible Probing Questionswhile students are exploring:1. How is the simulationsimilar/different fromreal life?1. The simulation showsarrows that can’t beseen in real life. Thesimulation usessimilar materials towhat we could do anexperiment with.2. The simulation doesn’t19
EXPLORATION Time: 30 minutesWhat the Teacher Will Do Probing Questions Student ResponsesPotential Misconceptions2. What are a fewlimitations of thesimulation?3. How do you thinkfriction affects themotion of an object?4. Give an example of ascenario where youexperienced what ishappening in thesimulation.5. If you wanted to pushsomething very farwith little force, whatsurface would youprefer?6. Besides ice, what isanother example of asurface little friction?What do we use thatsurface for?7. How does the size ofthe push relate to theacceleration of thecrate?8. When do you thinksimulations are usefulshow all of the forcesthat might act on anobject.3. Friction slows an objectdown.4. Sliding across the floorwith socks.5. Ice.6. Air hockey table, metal(slides onplayground), etc.7. Bigger push results in agreater acceleration.8. To show things thatcan’t be seen, to dolots of trails.20
EXPLORATION Time: 30 minutesWhat the Teacher Will Do Probing Questions Student ResponsesPotential Misconceptionsfor scientists?9. How could you designan experiment to testwhat you see in thesimulation?9. Various answers.EXPLANATION Time: 15 minutesWhat the Teacher Will Do Probing Questions Student ResponsesPotential MisconceptionsLet’s discuss our results fromour exploration.Negative values appear whenwe push the crate to the left,because we use a Cartesian-coordinate system to plot andjustify positive/negativevalues, the right correspondsto a positive direction whilethe left corresponds to anegative direction.1. What did you noticeappear on the screenas you attempt to pushthe box?2. As you pushed thecrate to the right, didpositive or negativevalues appear in theforce dialog box?3. How about as youpushed the crate to theleft?4. Why do you seenegative values?1.Arrows.2. Positive values.3. Negative values.4.Because the box wasmoving to the left.21
EXPLANATION Time: 15 minutesWhat the Teacher Will Do Probing Questions Student ResponsesPotential MisconceptionsCorrect, we have arrowspointing in oppositedirections. These arrowsrepresent the forces acting onan object. These forces (orarrows) are very importantwhen studying what happensas we push the crate.The simulation doesn’t showthe force of gravity or theforce of the ground pushingup on the crate.The force that opposesmotion is friction and you sawthat it points in the oppositedirection of the motion of theobject.5. What more can you tellme about the arrows,such as, the length ordirection of them?6. What force(s) are notshown on thesimulation?7. As you slowly drag themouse, what do younotice about the lengthof the Applied Forceand Friction Force?8. What did you noticeabout the length of thearrows once you’veapplied enough forceto push the crate?9. How do you think the5.The applied force arrowis pointing in thedirection of the push.The friction forcearrow is opposite ofthe applied forcearrow.6. The force of gravity, aforce pushing up.7.Both arrows appear toget longer.8. The applied forcearrow (orange) is nowlonger than thefriction force arrow(red).22
EXPLANATION Time: 15 minutesWhat the Teacher Will Do Probing Questions Student ResponsesPotential MisconceptionsThe crate is in motion so theforces are unbalanced and wesaw that there was a totalforce arrow present. Becausethis arrow is on the screen weknow that the net force onthe object is nonzero.Remember that thesimulation shows the netforce as the total force arrow.As we noted earlier, theforces acting on an object arein balance if that object is atrest or not accelerating. Inour case, even though wewere increasing the amountof applied force, the box stillremained at rest until acertain amount of force wasreached.simulation shows thenet force?10. If the forces areunbalanced, what dowe know about thesum of forces?11. Are the forces inbalance or unbalancedwhen the crate moves?How do you know?12. How does the directionof the total force arrowrelate to the directionthe crate moves?9.With the sum of forces.10.They are not zero.11. Unbalanced becausean unbalanced forceresults in themovement of anobject. The net forceis not zero.12. The object moves inthe direction of thetotal force at first,then slows downwhen the total forcearrow changes.23
EXPLANATION Time: 15 minutesWhat the Teacher Will Do Probing Questions Student ResponsesPotential MisconceptionsAt the beginning, the objectmoves in the direction of thetotal force arrow. This isbecause there must beenough force present toovercome the force of friction(the force in the oppositemotion of the applied force).However, the object slowsdown when frictionovercomes the motion of theobject and the total forcearrow points in the oppositedirection of the motion of theobject.Since ice is an almostfrictionless surface, thesimulation treats ice as africtionless surface. We donot have friction acting onthe crate.The object doesn’t slow downin the simulation because13. When the surface is icewhat force is missingfrom when the surfacewas wood?14. How is the motion ofthe crate differentwhen ice is thesurface? Why?15. If the brick wallsweren’t there what doyou think wouldhappen to the motionof the crate?13. Friction force.14. The object doesn’tslow down.15. It would continuegoing!24
EXPLANATION Time: 15 minutesWhat the Teacher Will Do Probing Questions Student ResponsesPotential Misconceptionsfriction isn’t present. Frictionopposes the motion of anobject by slowing it down.Exactly, that is Newton’s FirstLaw of Motion, which is anobject at rest remains at restunless acted upon by anoutside force and an object inmotion remains in motionunless acted upon by anoutside force.Exactly, a small force, orpush, results in a slowerchange in the objects speed.Correct, a large force, orpush, results in a greater16. If the brick walls werenot there anymore,what would the motionof the crate look like?17. How much does thecrate’s speed changewhen providing a littleforce?18. Why is there not muchchange in the object’sspeed when a smallforce is applied? Whatevidence do you have?Explain.19. How much does thecrate’s speed changewhen providing a bigpush? What evidencedo you have? Explain.16. The object wouldcontinue to move.17. A small force or pushresulted in a slowerchange in the objects’speed.18. We only provided asmall force.19. Largely. There is alarge change.25
EXPLANATION Time: 15 minutesWhat the Teacher Will Do Probing Questions Student ResponsesPotential Misconceptionschange in the objects speed.Correct, the amount of forceapplied affects how fast orslow an object changesspeed. In other words, ifacceleration is defined as howfast an object changes speed,then a greater force causesgreater acceleration, while asmaller force causes lessacceleration.Let’s go back to our Questionof the Day: “How can forcesaffect the motion of anobject?” In your pairs, comeup with three ways forces canaffect the motion of anobject.Call on students forresponses. Make surestudents include: force,balanced and unbalanced,speed, friction andacceleration in theirdiscussion.Now that we have20. Why is there such alarge change in theobject’s speed?21. What generalstatement can wemake about therelationship betweenthe applied force andhow fast an objectchanges speed?20. We provided a bigpush, or a much largerforce.21. A small applied forcecauses a slowerchange in the object’sspeed. A large appliedforce causes a fasterchange in the object’sspeed.26
EXPLANATION Time: 15 minutesWhat the Teacher Will Do Probing Questions Student ResponsesPotential Misconceptionsexperimented withcomputers, lets discuss theimpact of computers duringthis lesson. Scientists usecomputer simulations, like theone we used today, to predicthow objects would behavewhen an outside force isapplied.I want you to turn to yourpartner and discuss threeadvantages of using acomputer simulation andthree disadvantages to usinga computer simulation. Thinkabout how the computersimulation was different fromour demos.A few of the advantages ofusing the simulation are thatit allows us to view the forcesacting on an object. We alsodon’t have to have all thematerials in front of us. Wecan model different aspectsthat we may not be able to inthe classroom (such as, usingice).22. What advantages doyou think thesimulation has?23. What are a fewdisadvantages?22. We can view theforces on an object asthey are representedby arrows. It alsoallows us to usematerials that wedon’t have in ourclassroom.23. It doesn’t considersome of the forcesthat can act on theobject. It can bedifficult to use.27
EXPLANATION Time: 15 minutesWhat the Teacher Will Do Probing Questions Student ResponsesPotential MisconceptionsDisadvantages include thatthe simulation doesn’tconsider some of the forcesthat are acting on the object.An example would be that itdoesn’t take into account airresistance.ELABORATION Time: 10 minutesWhat the Teacher Will Do Probing Questions Student ResponsesPotential MisconceptionsLet’s relate forces to acurrent event.Teacher begins “TurkeyEarthquake” PowerPoint.Recently, on October 23rd, astrong earthquake hit Turkey.Show Slide 2.Tectonic plates collidingcause earthquakes.Show Slide 3. Point outdifferent tectonic plates.1. Where is the countryTurkey?2. What do you thinkcauses earthquakes?3. What two plates onthis map could havebeen responsible forthe earthquake inTurkey?1. Europe, near Africa,near Asia.2. Tectonic platescolliding.3. The Arabian andEurasian plates.28
ELABORATION Time: 10 minutesWhat the Teacher Will Do Probing Questions Student ResponsesPotential MisconceptionsThe Arabian plate pushingagainst the Eurasian platecaused the earthquake. Theearthquake had a magnitudeof 7.1 so it was a relativelystrong quake.Show Slide 4.The earthquake was ineastern Turkey in the cityErcisShow Slide 5.Here is an image of a “shakemap.”The different colors representhow strong the “shake” couldbe felt. This map looks similarto a weather map you mightsee on the news or on theInternet. The orange areasare where severe shakes werefelt and the green is where avery light shake was felt.Earthquake engineers areresponsible for constructingbuildings that can withstandearthquakes. Althoughbuilding designs haveprogressed a lot in the past4. What do you think thedifferent colorsrepresent?5. What do you think anearthquake engineerdoes?4. How the earthquakefelt, it’s a key.5. Design things towithstandearthquakes.29
ELABORATION Time: 10 minutesWhat the Teacher Will Do Probing Questions Student ResponsesPotential Misconceptionscentury, the earthquake inTurkey caused many buildingsto collapse.Show Slide 6.According to the WashingtonPost, two thousand buildingshave collapsed and thirtyseven hundred are unfit forhabitation.Now we are going to modelan earthquake with blocksand cardboard.I want you to make threebuildings of different sizes.Each row of blocks willrepresent a story on abuilding.You will construct your toweron top of a cardboard boxand then you will “shake theground” by moving thecardboard box slowly backand forth. In your sciencejournals, please record yourobservations.6. What could I do withthe cardboard and theblocks?7. What could the rows ofblocks represent?Questions to ask as studentsbuild their earthquakes:1. When are the forces6. Model an earthquake!7. Different floors,different buildings.1. Unbalanced.30
ELABORATION Time: 10 minutesWhat the Teacher Will Do Probing Questions Student ResponsesPotential Misconceptionsbalanced andunbalanced duringyour earthquake?2. What did you noticeabout how the size ofthe tower relates tothe movement of thetower?3. What forces are actingon the tower beforeyou pull thecardboard?4. How is this modelsimilar/different from areal earthquake?5. What changes couldyou make to yourtower design so that itdoesn’t fall?6. What type of materialdo you think would bebest for anearthquake?2. Answers vary onstudent designs.3. Gravity and upwardforce from the table.4. The blocks aren’tattached to eachother like in a realbuilding. There mightbe buildings besidethe other buildingsthat will bump intothem.5. Connect the blocks,use other materials.6. Something that isn’trigid and could bend.Something that issturdy, etc.31
EVALUATION Time: 5 minutesWhat the Teacher Will Do Probing Questions Student ResponsesPotential MisconceptionsPass out “EvaluationQuestions.”32
Name: _____________________Forces and Motion ExperimentMaterials• 1 playing card• 1 cup• 1 pennyProcedure1. Set the playing card on top of the cup.2. Set the penny on top of the playing card.3. Flick the playing card.4. Observe what happens!Questions1. What force(s) acted on the playing card?2. What force(s) acted on the penny?3. In this experiment, what was at rest?4. In this experiment, what was in motion?5. Why didn’t the penny move sideways as much as the card?Newton’s 1stLaw:An object at rest remains at _______ unless acted upon by an ______ force and an object in motionremains in _______ unless acted upon by an ______ force.33
Name: ________________________Forces and Motion Basics PhET Simulation1) Fill in the following blanks with your partner.2) Play with the simulation for five minutes. Be prepared to share what you have discovered!3) a) Explore how the “Applied Force” and “Friction Force” arrows change as you apply differentamounts of force.b) Use the table to record your observations.How muchforce isapplied?Is the applied force larger, smalleror equal to the friction force?The forces onthe crate are…(circle one)Observations – whatevidence do you havefor your selections?balancedunbalancedbalancedunbalancedbalancedunbalanced4) a) Explore how the “Total Force” arrow depends on how the crate moves.b) As the object moves, what happens to the total force arrow?______________________________________________________________________________________________________________________________________________________________________________________________________5) a) Explore what happens when you change the surface.b) Fill in the table with your observations.34a) The total force is the _______________ of all the forces.b) An object’s acceleration is an object’s _____________ in speed.c) Friction is a force that ________ the motion of an object.
Surface ObservationsIce (no friction)Frictionc) The simulation assumes that ice is a frictionless surface. To have a truly frictionlessenvironment what else would you need to consider?______________________________________________________________________________________________________________________________________________________________________________________________________6) a) Explore how the crate’s speed changes as you apply more and less force to the crate.b) Fill in the table with your observations.Size of push Amount of change in speed(circle one)large change in speedsmall change in speedlarge change in speedsmall change in speedc) What can you say about how the amount of force applied affects an object’s acceleration?______________________________________________________________________________________________________________________________________________________________________________________________________35
Name: _________________________Forces and Motion Evaluation Questions1. When the forces on an object are balanced, what is the total force?a) 1 Newton to the left.b) 1 Newton to the right.c) Unable to determine without knowing the forces involved.d) 0 Newtons.2. An object experiences a force of 5.0 Newtons pushing towards the left and a force of 5.0 Newtonspushing towards the right. These forces area) balanced.b) unbalanced.c) complimentary.d) inverse.3. An object is initially at rest on a frictionless surface. We apply a force of 1.0 Newton to the right.What happens?a) The object was not moving, so it starts moving to the right.b) The object pushes back with a force of 1.0 Newton, so nothing happens.c) The object moves to the right and will continue to move to the right at a constant speed.d) The object slows down while moving to the right.4. The table below shows the acceleration of a 50kg crate in response to applied forces. Identifywhich acceleration should be used in the missing spot.a) 0 m/s2b) 0.67 m/s2c) 7.02 m/s2d) 1.33 m/s2Applied Force (N) Acceleration (m/s2)0.5 ?1.0 2.672.0 5.333.0 85. To test how an object moves without friction, you musta) make sure the object does not touch anything (including air).b) put the object on ice.c) take away friction by lubricating the surface the object is on.d) make the object move very fast to reduce the effect of friction.6. How did Galileo’s study of motion differ from Newton’s? Why do we use Newton’s physics todayinstead of Galileo’s?36
Photo of Sir Isaac Newton. Source: http://www.newton.ac.uk/art/portrait.html
Photo of Galileo Source: http://www.nmm.ac.uk/mag/pages/mnuExplore/PaintingDetail.cfm?ID=BHC2700
Question of the DayHow canforces affectthe motion ofan object?
Name: ________KEY_________Forces and Motion ExperimentMaterials• 1 playing card• 1 cup• 1 pennyProcedure1. Set the playing card on top of the cup.2. Set the penny on top of the playing card.3. Flick the playing card.4. Observe what happens!Questions1. What force(s) acted on the playing card?Gravity, my hand.2. What force(s) acted on the penny?Gravity, the playing card transmitted a small part of the force from my hand.3. In this experiment, what was at rest?The cup, playing card and penny before I flicked, the cup when I flicked the playing card, andthe cup, playing card and penny after they fall.4. In this experiment, what was in motion?When I flicked the playing card, the card and penny were in motion. They stayed in motionuntil they hit the ground.
5. Why didn’t the penny move sideways as much as the card?The friction between the penny and card was small, so only a small amount of the force of myhand was transmitted. Since it was a small amount of force, the penny only moved a little.Newton’s 1stLaw:An object at rest remains at _rest__ unless acted upon by an _unbalanced_ force and an object inmotion remains in _motion_ unless acted upon by an _ unbalanced _ force.
Name: __________KEY______________Forces and Motion Basics PhET Simulation1) Fill in the following blanks with your partner.2) Play with the simulation for five minutes. Be prepared to share what you have discovered!3) a) Explore how the “Applied Force” and “Friction Force” arrows change as you apply differentamounts of force.b) Use the table to record your observations.How muchforce isapplied?Is the applied force larger, smalleror equal to the friction force?The forces onthe crate are…(circle one)Observations – whatevidence do you havefor your selections?200NewtonsEqual to the friction force, in theopposite direction. balancedunbalancedThe box doesn’t move,and the total forcearrow is zero.-400NewtonsEqual to the friction force, in theopposite direction.balancedunbalancedThe box doesn’t move,and the total forcearrow is zero.500NewtonsGreater than the friction force, inthe opposite direction.balancedunbalancedThe box moves, and thetotal force arrow pointsto the right.4) a) Explore how the “Total Force” arrow depends on how the crate moves.b) As the object moves, what happens to the total force arrow?__If the crate isn’t moving, the total force arrow is zero. The force arrow points to the right if apositive force is applied and the object is moving. It points to the left if a negative force isapplied and the object is moving. When we stop applying the force, the force arrow points inthe opposite direction of motion, and is the same size all thetime._______________________________________a) The total force is the ____sum________ of all the forces.b) An object’s acceleration is an object’s ____change___ in velocity.c) Friction is a force that _reduces_ the motion of an object.
5) a) Explore what happens when you change the surface.b) Fill in the table with your observations.Surface ObservationsIce (no friction) Any force will cause the crate to move and it only stops if itcollides with something else.Friction The crate must get a certain amount of force to start movingand when the force stops, friction causes the crate to slowdown.c) The simulation assumes that ice is a frictionless surface. To have a truly frictionlessenvironment what else would you need to consider?The object touches nothing.___________________________________________________________________________________________________________6) a) Explore how the crate’s speed changes as you apply more and less force to the crate.b) Fill in the table with your observations.Size of push Amount of change in speed(circle one)large change in speedsmall change in speedlarge change in speedsmall change in speedc) What can you say about how the amount of force applied affects an object’s acceleration?__The greater the unbalanced force applied on an object, the greater the acceleration of theobject.______________________________________________________________________________________________________________
Name: _________________________Forces and Motion Evaluation QuestionsKey – numbers reference learning goal #1. When the forces on an object are balanced, what is the total force? (3)a) 1 Newton to the left.b) 1 Newton to the right.c) Unable to determine without knowing the forces involved.d) 0 Newtons.2. An object experiences a force of 5.0 Newtons pushing towards the left and a force of 5.0 Newtonspushing towards the right. These forces are (1)a) balanced.b) unbalanced.c) complimentary.d) inverse.3. An object is initially at rest on a frictionless surface. We apply a force of 1 Newton to the right.What happens? (2, 4)a) The object was not moving, so it starts to move towards the right.b) The object pushes back with a force of 1 Newton, so nothing happens.c) The object moves to the right and will continue to move to the right at a constant speed.d) The object slows down while moving to the right.4. The table below shows the acceleration of a 50kg crate in response to applied forces. Identifywhich acceleration should be used in the missing spot.a) 0 m/s2b) 0.67 m/s2c) 7.02 m/s2d) 1.33 m/s2Applied Force (N) Acceleration (m/s2)0.5 ?1.0 2.672.0 5.333.0 8
465. To test how an object moves without friction, you must (5)a) make sure the object does not touch anything (including air).b) put the object on ice.c) take away friction by lubricating the surface the object is on.d) make the object move very fast to reduce the effect of friction.6. How did Galileo’s study of motion differ from Newton’s? Why do we use Newton’sphysics today instead of Galileo’s? (6)Galileo thought the gravity he measured on Earth was unique; Newton showed thatthe force of gravity could be calculated for any place in the universe. Newton’sphysics applies to more situations, which is why we use it.