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Dr. M. H. Suckley & Mr. P. A. Klozik Email: [email protected] Additional copies of the Conference Handout may be Obtained at: http://www.ScienceScene.com (The MAPs Co.) Motion A Teacher Designed Unit Based Upon the Michigan Benchmarks I. Introduction 4 II. Michigan Benchmarks 4 III. Unit Objectives 5 IV. Prerequisite Skills and Formative Evaluation 5 V. Instructional Unit 6 VI. Summative Evaluation 21 II. Michigan Benchmarks for Motion Prerequisit e Skill force s V=d/ t F=mx a Futur e Unit 11 1. Describe or compare motions of common objects in terms of speed and direction. 2. Describe how forces (pushes or pulls) are needed to speed up, Key concepts: Words--east, north, south, right, left, up, slow down, stop, or changewest, the direction of a moving object. down. Speed words--fast, slow, faster, slower. 3. Key Qualitative describe andincompare motion in two concepts: Changes motion--speeding up, dimensions. slowing down, Real- world contexts: Motions ofpull, familiar objects in two turning. Common forces--push, friction, gravity. Size of in 4. Key Relate motion of objects to unbalanced and balanced forces concepts: Twodimensional motion--up, down, curved path. dimensions, including rolling or change is related to strength of thrown push orballs, pull. wheeled vehicles, two dimensions. Speed, direction, change in speed, change in direction. sliding objects. 5. Design strategies forPlaying moving objects by application of forces, including Realworld contexts: ball, moving chairs, sliding objects. Key concepts: Changes in motion and common forces--speeding Realworld contexts: Objects in motion, such as thrown balls, the use of simple machines. up, slowing down, pull, friction, gravity, magnets. roller coasters, carsturning, on hills,push, airplanes. Constant motion and balanced forces. Additional forces-Realworld contexts: Changing direction--changing direction of a attraction, repulsion, action/ the reaction pair (interactionthe force), billiard ball, bus turning corner;ischanging speed--car speeding up, buoyant force. Size of a change related tothe strength of a unbalanced rolling ball slowing down, magnets changing the motion of objects, force and mass of object. walking, swimming, jumping, rocket motion, objects resting on a table, tug-world of- war. Realcontexts: Changing the direction--changing the direction of a billiard ball, bus turning a corner; changing the speed--car speeding up, a rolling ball slowing down, magnets changing the motion of objects, walking, swimming, jumping, rocket motion, objects resting on a table, tug- of- war. III. Unit Objectives for Motion 1. Given the following list of terms, identify each term's correct definition. Conversely, given the definition, identify the correct term. acceleration, constant acceleration, force, inertia, kinetic energy, linear motion, mass, momentum, speed, time, velocity, weight, 2. Describe how forces (pushes or pulls) are needed to speed up, slow down, stop, or change the direction of a moving object by: 3. Describe and compare motion in two dimensions. Given the distance (x), the time (t) and the formula v = x / t, calculate the speed (v) of any object moving in a straight line with constant velocity. (Newton's First Law) 4. Relate motion of objects to unbalanced forces in two dimensions. (Newton’s Second Law) a. Given the formula f = m x a, calculate the force acting on an object with a mass (m), moving with a constant acceleration (a). b. Given the formula a = (vfinal - vinitial) / time, compute the acceleration of an object moving in a straight line with constant acceleration. 5. Relate motion of objects to balanced forces in two dimensions. Given an object at rest or in motion identify the forces acting on the object. (Newton's third Law of Motion.) 5 IV. Prerequisite Skills (skills learners must posses to be successful) 1. Linear measurement skills 2. Use of a stopwatch 3. Computational skills 4. Recording data 5. Cooperative work skills 6. Verbal Skills 7. Communication 8. Reading comprehension 8 Formative Evaluation (Determining if the learner is being successful along the way) Observation of group interaction Instructor questions directed to individual students Ongoing review of data obtained though experimentation Summative Evaluation (Determining How Successful the Learner has been Mastering the Unit) Laboratory Report Comprehensive exam essay forced answer (multiple choice, fill in the blank) 2 V. Instructional Unit A. Forces 1. Finding the Forces 2. Types of Force 6 10 B. Motion in two dimensions – (Newton’s 1st ) 1. Observing Motion 2. Inertia - Fundamentals 12 13 14 C. Motion - unbalanced forces in two dimensions (Newton’s 2nd) 1. Observing Acceleration 2. The affect of Mass on Acceleration 15 16 17 D. Motion - balanced forces in two dimensions (Newton’s 3rd ) 1. Equal and Opposite 2. Equal and Opposite another Look20 18 19 20 Finding The Forces Activities 1. Have someone hold a 500-gram hooked mass (HM) in their outstretched hand. Use the arrows so indicate all the forces acting on the HM. 2. Hang the hooked mass from a rubber band. Use the arrows to indicate the forces acting on the HM. 3. Hang the hooked mass from a string. Release the string to drop the HM. (Please catch it.’) 4. Place the HM on a platform spring scale. 5. Place the hooked mass on a soft sponge or piece of foam rubber. The sponge should be soft and about the size of the HM. Push the HM with a horizontal force. The force you apply should be large enough to affect the sponge, but not so large as to make the sponge or the HM slide. 6. Place a coin at the edge of the table. Give it a flick with your finger so it hits the floor some distance away. Make a free-body diagram showing the forces acting on the coin (1) setting on the table, (2) while your finger is in the process of flicking it and (3) while it is moving through the air. 7. Out of a 3 x 5 card, make a device that allows you to flick one coin at the same time that you simply drop a second coin. 6 Finding The Forces Activities 2. 7. 1. 1. 6. 3. 2. 3. 4. 4. 5. 6. 5. 8 7. Finding The Forces 1. At Rest 5. At Rest 7 2. At Rest 3. Acceleration 6. At Rest and Accelerating 4. At Rest 7. Accelerating Types of Forces A force is defined as any push or pull that results in accelerating motion Circular - When objects move in circles, a force acts with a direction that is toward the center of the circle. We call this direction CENTRIPETAL Circular Gravitational - All objects attract all other objects with a force called gravitational force. Electromagnetic - Electric forces act on objects when the object carries a net electric Gravitational charge or a non-uniform distribution of charge. Magnetic force is also observed around a moving electric charge and act on those charges. Physicists believe that all magnetic forces are produced by moving charges. Electromagnetic Frictional - Frictional forces are often classified as sliding, rolling, static and fluid. Sliding and rolling frictional forces result when solids in contact pass by each other. Static frictional force results when solids are in contact, at rest and when a force or forces are trying to cause them to move with respect to each other. Fluid frictional force results when a solid is moving through a gas or a liquid. Frictional Normal Normal - “Normal” means “perpendicular to”. Whenever an object is placed on a surface, a force acts normal to the surfaces in contact. This causes the supporting surface to sag. Since this sagging is slight, it often goes unnoticed. However, it is always there and the resulting force of the surface attempting to return to its original position is perpendicular to the surface. Tension Tension - Tension force is the force exerted by a string, spring, beam or other object which is being stretched compressed. The electric forces among the molecules give rise to the force. 7 Newton’s First Law An object stays at rest or continues to move in a straight line at a constant speed unless acted on by a force. V=d/t Time Observing Motion Distance t0 t1 .50-meters Finish Point Starting Point Trial 1 Sec. Trial 2 Sec. Trial 3 Sec. Average Sec. Distance meters Velocity Meters/sec V=d/t 0.43 0.44 0.43 0.44 .500 1.14 0.31 0.32 0.32 0.32 .350 1.09 Equipment Set-Up 6 Jump 2 1 0 Time • The interval between two events. 00 03 00 25 00 S T A R T 1 S T O P 0 Distance • The interval between two objects. S T A R T S T O P 0 Inertia Jump 2 Applying Small Force Applying Large Force What is Inertia? Answer: The tendency of matter to remain at rest if it is at rest or, if moving, the tendency to keep moving in the same direction unless acted upon by some outside force. 0 2 Newton’s Second Law When a force acts on a moving object, it will accelerate in the direction of the force dependent on its mass and the force. F=mxa Observing Acceleration - of a Toy Car .500-meter .350-meter .150-meter t2 t0 t1 B A 0.350-m t0→ t1 0.500-m t0→ t2 0.150-m t1→ t2 (t2- t1) First time trial 0.32 0.43 0.11 Second time trial 0.31 0.44 0.13 Third time trial 0.32 0.43 0.11 (4) Average Time 0.32 0.44 0.12 (5) Average velocity v = d / t 6) Time (when average velocity occurred) V1 (.350/.32) 1.09-m/s V2 (.150/.12) 1.25-m/s Position A TA = (t1 + t0) /2 0.16-sec Position B TB = (t2 + t1) / 2 0.38-sec (6) v = change in adjacent velocity v= v2 – v1 0.16-m/s (7) T = change in time between adjacent velocity t = TB – TA 0.22-sec (8) a = acceleration between points a = v / t 13 Starting Point .73-m/s/s .73-m/s2 The Affect of Mass on Acceleration 8 Battery Trial 1 Sec. Trial 2 Sec. Trial 3 Sec. Average Sec. Distance meters Velocity Meters/sec Without 0.43 0.44 0.43 0.44 .500 1.14 With 0.31 0.32 0.32 0.32 .500 1.09 Newton’s Third Law Every Action Has An Equal And Opposite Reaction. f1 = f 2 Newton’s Third Law Equal and Opposite Slippery Plastic 1. Crumple the plastic until it looks very wrinkled 2. Place the slippery plastic on a solid, flat surface. 3. Place the car on top on the slippery plastic. 4. Start the car and observe the car and the slippery plastic. 4 Equal and Opposite, Another Look 1. Place two soda cans on a flat surface approximately 25-cm apart. 2. Place the plastic on top of the soda cans. 3. Place the car on top on the plastic as shown. 4. Start the car and carefully observe the car and the plastic. 3 Summative Evaluation The Class Debriefing - Did we Get There? If we did 1. The Laboratory Report 2. The Exam 3, Celebration If we did not 1. Re-teach 2. Provide alternate activities 3. Retest The Stopwatch We Had A Great Time