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Force and Motion
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A list of children's ideas about Energy & Thermal, compiled by Professor Robin Millar from the University of York, using Rosalind Driver et al.’s Making Sense of
Secondary Science, Randall Knight’s Five Easy Lessons, The Victoria Science Continuum, and his own knowledge of the area. These are matched to direct quotes
from the literature in each tab of this spreadsheet. The "count" indicates how many times a match has been found.
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CountReferenceIdea
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1fm1Many younger pupils have only an intuitive idea of speed, and cannot relate it to information on distance and time.
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1fm2Many pupils do not clearly distinguish the ideas of instantaneous and average speed
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11fm3Many pupils have an unclear idea of acceleration, and cannot reliably separate it from speed.
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0fm4Many pupils think acceleration always means increasing speed (and that decreasing speed is called deceleration).
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0fm5Many pupils have difficulty separating the ideas of distance and displacement.
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2fm6Many pupils conflate velocity with speed and believe they (whether instantaneous or average) are always the same size.
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1fm7Many pupils have difficulty recognising that the direction of the change of velocity of an object is not necessarily the same as the direction of its velocity.
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2fm8Many pupils think that an object’s acceleration is always in the direction in which the object is moving.
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0fm9Many pupils think that, if an object has a speed of zero (even instantaneously), it has no acceleration.
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0fm10Some pupils interpret distance-time and speed-time graphs as though they were ‘pictures’ of a situation.
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1fm11Some pupils are unable to translate the verbal description of an object's motion into a graphical description and vice versa.
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0fm12Many pupils have difficulty in describing, or calculating, speeds from a distance-time graph, especially one that is non-linear.
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0fm13Many pupils have difficulty in describing, or calculating, accelerations from a speed-time graph, especially one that is non-linear.
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3fm14Many pupils think that a compact object (such as a ball or a stone) falls at a constant speed which depends on how heavy it is.
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4fm15Many pupils think a heavier object will fall faster than a lighter one of the same general shape or size. (MSSS)
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3fm16 Many younger pupils can use the word ‘force’ (to mean a push or a pull) and think that a force is needed to get a stationary object moving. (MSSS)
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0fm17Some younger pupils may not think of a kick or a throw as involving a ‘push’ or ‘pull’. (MSSS)
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14fm18Many younger pupils think forces can only be exerted by living things and some machines, but not by inanimate objects (such as floors or walls).
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3fm19Many pupils have difficulties in using arrows to indicate the direction and point of action of a force. (MSSS) (e.g. thinking that it matters if the tip or end of the arrow is at the point of action)
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9fm20Many pupils do not see forces as arising from (and during) an interaction between two objects, and always as pairs of equal forces, one acting on each of the interacting objects. (MSSS)
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2fm21Many pupils who do recognise that forces arise in pairs think that the two forces in a pair may differ in size (e.g. they think a larger object exerts a bigger force on a smaller object than vice versa).
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0fm22Many pupils do not recognise that the forces in an interaction pair always act on different objects, and confuse the balanced forces on a stationary object (such as a box sitting on the floor) with the equal forces of an interaction pair.
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3fm23Many pupils see friction as a phenomenon, rather than as a force. (MSSS)
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2fm24Some pupils think that friction arises only when there is motion. Few understand that the size of the friction force matches the externally applied force, up to a limit (for any given pair of surfaces).
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1fm25Some pupils confuse friction and normal reaction, as both arise from an interaction between an object the surface it is sitting on. (MSSS)
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4fm26Many pupils are unable to identify correctly the forces acting on each object in a situation where two or more objects interact (i.e. to construct a free-body diagram).
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10fm27Some pupils think that ‘at rest’ is a natural state in which no forces are involved. (Vic)
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18fm28Many pupils think that a force is needed to keep an object moving with a constant speed. A constant speed results from a constant force – and the bigger the force on an object, the faster it moves. (MSSS)
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29fm29Many pupils think of a force as a property of objects, not as something that arises when two objects interact. A moving object has a force within it that keeps it going. It is given this force by whatever pushes or pulls it to get it moving. It stops when its force is used up. (MSSS)
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9fm30Many pupils think that a heavy moving object has more force than a light one, and that a fast-moving object has more force than a slow-moving one.
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14fm31Most pupils think that, if an object is moving, there must be a force in the direction of its motion.
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3fm32Many pupils cannot correctly identify the forces acting on an object that has been set in motion but is slowing down.
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1fm33Many pupils think that the law of conservation of momentum in collisions applies only to situations in which one or more objects is visibly moving after the collision (and not, for example, to a snowball hitting a wall).
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1fm34Few pupils understand how conservation of momentum in an interaction follows from Newton’s Third Law of motion and the fact that the time interval during which the forces act is necessarily the same for both objects.
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4fm35Some younger students do not associate the phenomenon of weight with the force of gravity. (Vic)
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2fm36Many pupils think of mass and weight as alternative words for the same property.
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4fm37Many pupils see falling as ‘natural’ and not requiring an explanation. (MSSS)
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4fm38Many pupils think that the force of gravity on an object will increase as it is moved higher, further away from the Earth’s surface. (MSSS)
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7fm39Many pupils think that an object beyond the Earth’s atmosphere (in space) does not experience a force of gravity.[3] (MSSS)
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9fm40Some pupils think that gravity requires the presence of air (so there is no gravity on the Moon, or in space). (MSSS)
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3fm41Many pupils think the resistance of an object to changes in its horizontal motion is due to its weight (rather than its mass).
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3fm42Many pupils are unable to apply Newton’s Second Law (the acceleration of an object is proportional to the resultant force acting on it, and is always in the direction of the resultant force) to examples of motion in 2D (circular motion, projectile motion), or to 1D situations where the speed of an object is decreasing.
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3fm43Many pupils think the downward motion of a projectile will be affected by its horizontal motion (in particular that an object projected horizontally will fall less quickly than one that is simply dropped)
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2fm44Many pupils think that an object that is moving along a curved path will continue to follow a curved path when its motion becomes unconstrained.
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3fm45Many pupils think that an object moving in a circle experiences a force away from the centre of the circle (a centrifugal force).
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Additional misconceptions found by RIS teachers:
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Force means to coercion, resistance and actionWatts, 1983; Osborne. Schollum and Hill, 1981; Shevlin 1989
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trouble with vector addition, trouble with realising that velocity is a vectorfm7?White, 1983fm4
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"Things go in the direction that you hit them [even if they already have momentum]"fm31?White, 1983fm7
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many people believe falling objects that were moving forwards fall straight downfm43?McCloskey, 1983fm48
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a few people believe falling objects that were moving fall backwardsfm43?McCloskey, 1983fm48
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"Many students clearly did not know that objects move in straight lines when no external forces acts on them"fm29?McCloskey, 1980fm29
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"An object moving through a curved tube acquires a "force" or "momentum" that causes it to continue in curvilinear motion. The force or momentum eventually dissipates and the objects trajectory becomes straight."
fm29?McCloskey, 1980fm44, but the opposite?
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Some students (15%) are unaware of the difference between weight and gravityfm35?Berry, 1993fm35
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Some students believe the force on a ball "gets less as it goes up"fm39?Gilbert, 1982fm29
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Some students suggested comet being ‘pushed away’ by the Sun.space list?Emmett, 2009
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Some pupils do not distinguish between the size of an object and its weightSmith et al. (1985)
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Some pupils think gravity only acts if an object is moving downwardsBerry (1993)fm29
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Surfaces which stop an object from falling give an object 'support', but this is not identified as a forceBliss et al (1989)
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Some students do not consider acceleration the time interval when considering acceleration. Students do not compare acceleration as a ratio of change in velocity/change in time
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Some students are not able to make a distinction between force and energy
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Notes:
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1 References: MSSS: Driver et al. (1994), Making Sense of Secondary Science; Vic: Victoria Science Continuum; McD (Lillian McDermott review article in ICPE 1998 eBook), 5EL: Randall Knight, Five Easy Lessons..
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[1] I have opted for ‘force’ rather than ‘resultant force’ here, because some studies report students thinking that a moving object that is slowing down must have a force in the direction of motion, even though they also think there is a larger force in the opposite direction.
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[2] This seems at odds with the statement immediately above. This is just one example of the widely reported finding that many pupils’ ideas about forces and motion are inconsistent.
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