Research On Core Ideas Of Force And Their Leaniing Progressions In Chinese High-school Physics

The concept of teaching has been the main center of science education, graspingand applying academic knowledge depends on whether students mastered the themeand essence of the subject matter, and this part reflected in the conceptual knowledgewhich is the highly abstract and on behalf of significance in the disciplinary. As a keyconcept of connecting the whole disciplinary or the branch of disciplinary, coreconcept has become an important area of research on international science education,part of the middle school curriculum standards in china also offered to help studentsunderstand the core concepts of discipline deeply. Learning is a gradual processacross in the process of teaching, and that requires coherence, step by step, fromsimplicity to complexity, concept learning more should follow this principle, the coreconcept of learning is in particular. Learning progressions are ordered descriptionsabout how students’ understanding of core scientific concepts and its associatedmethods, skills, practices in the progress and development over time, revealing thecognitive processes and the development model of learning. In this research, theauthor studied on mechanics of high-school physics, through analyzing andcomparing curriculum standards of U.S. and China, combing and generalizing PEPhigh-school physics textbooks, and surveying views of the teachers in the school. Fivecore concepts were retrieved: force, motion, Newton’s first law, Newton’s second lawand Newton’s third law and so on. Then the author research on the five concepts withthe testing scale relying on the FCI. The280students as the research subjects are fromschools of provincial, municipal and county levels in area of Shijiazhuang City.Finally the author initially identified the concept of an advanced case by analyzing thetest results of each concept, based on two-dimensional type of correctrate-concentration.As above, the conclusions are obtained as follows:(2)The author builds learning progression for the core idea of “Force”.Level1: The stationary object or the objects that the direction of moving isconsistent with the direction of the force, and the objects keep uniform motion, then combined force acting on the object is zero, it is a state of equilibrium, if thereare only two forces acting on the object, the two forces are equal in magnitude andopposite in direction.Level2: The objects of the circular motion are affected by centripetal force. Thedirection of the force is always pointing to the center. Centripetal force is not actuallyforce, which is the resultant force acting on the object or individual component. Theobjects of the circular motion are not affected by any force in the direction ofmovement.Level3: If the objects of uniform speed linear motion accelerate, the direction offorce is same as the direction of movement; if the objects decelerate, the direction offorce is in contrast with the direction of movement. The objects of upward verticalprojectile motion, excluding resistance, rise slowly because of gravity, and fall fastalso because of gravity.Level4: How to force is regardless of the direction of motion, force is the reasonfor changing the state of motion of objects and not to keep the movement. The samedirection of the force is not necessarily as the direction of movement. If the directionof the force on the object is perpendicular to the direction of motion, and objectskeep uniform linear motion, then the object acted on a balance force, the direction ofthe force is vertical to direction of movement.(2) The author builds learning progression for the core idea of “motion”.Level1: Make the object horizontally uniform linear motion, only by gravity，seem the ground as the reference system, the trajectory is a parabolic.Level2: Objects fall by gravity and air resistance, without taking into accountthe resistance, objects freefall. Objects fall faster and faster, and unrelated to quality;the time of falling depends on the height of falling. If objects do parabolic motion atthe horizontal direction, of the same speed, the distance to starting points depends onthe height of falling, and unrelated to quality.Level3: The displacement of the object on uniform motion is equal at same timeintervals, and it keeps constant speed, and its acceleration is zero. If the displacementis greater, the speed is faster at equal time. If object on uniform speed linear motion, its instantaneous velocity of a position is equal to the average rate equal at theadjacent and same time intervals. There is always a moment that has the same ratebetween uniform motion and uniformly accelerated linear motion.Level4: If objects do parabolic motion at the horizontal direction, itstrajectory is a parabolic, and the concave of parabolic always points the directionof force, and the parabolic always begins at the location where the constant force is.Parabolic motion at the horizontal direction can be decomposed into uniform linearmotion in the horizontal direction and uniform accelerated linear motion in thevertical direction. The two movements have an isochronous.(3) The author builds learning progression for the core idea of “Newton’s firstlaw”.Level1: If the object with an initial velocity was not forced at the horizontaldirection or in the level desktop, its motion trajectory is a straight line and velocityremains unchanged.Level2: There are objects of circular motion in the horizontal plane leaving acertain height from ground, if no external force, they are still a linear trajectory, andremains unchanged.Level3: An object with initial velocity, the latter by the instantaneous force,velocity of the object remains constant.Level4: If objects keep parabolic motion at the horizontal direction, thetrajectory of them will be a straight line after they lose force at a certain point.(4) The author builds learning progression for the core idea of “Newton’s secondlaw”.Level1: The stationary object in the rough surface will keep a constant speed atthe horizontal direction after the external force at the constant level, then the resultantforce acting on the object is still the same zero, and acceleration is zero, and theresistance force in the horizontal direction is the external force.Level2: The objects in the external force are doing uniformly accelerated linearmotion. If the force was suddenly removed, the object will decelerate to a stopimmediately by the action of the resistance, resulting in an acceleration of a direction opposite to the movement.Level3: Objects do uniform linear motion on level ground, by the action of aconstant external force, and then a constant acceleration in the direction of the forcewill be produced. If the direction of the movement was same as constant force’s or atan acute angle, the object would have been accelerated; If the opposite or at an obtuseangle, the object will slow down first, and then accelerate at the opposite direction.Level4: The instantaneous impact force produces only an instantaneousacceleration.(5) The author builds learning progression for the core idea of “Newton’s thirdlaw”.Level1: the two stationary objects, one object force to another object, but alsoanother object force to the object, the size of the force is Unrelated to the mass of theobject, which are equal in magnitude and opposite in direction; when stops, it stops.Forces between two objects on a collision course are equal in magnitude and oppositein direction.Level2: One object pushed another object to accelerate; the forces between eachother are equal in magnitude and opposite in direction, acting on the same straightline.Level3: If two objects contact with each other and maintain the same speed, theforces at the direction of movement between the two objects do not exist.