Konzeption und Evaluation eines Kinematik/Dynamik-Lehrgangs zur ...

9 Abstract 267
to a described motion, no significant difference could be proved (ntreat = 211, ncontr = 188) (chapter
6.4.2.4). The fact that within this concept motions in one dimension were dealt with less than in
traditional instruction, and instead understanding for quantities was trained using two-dimensional
motions does therefore not influence the solution of these problems on motions in one dimension.
Things are quite different when it comes to asking about the direction of acceleration instead of
about the graph. In the case of tossing a coin vertically up into the air (with change of direction), the
direction of acceleration in the form of algebraic signs with a given coordinate system and in the
form of arrows was asked, so that the students had to make a decision between the conception of
�
“speeding up/slowing down” a = ∆ v / ∆t
(acceleration as a change in speed) and a conception of
� �
direction a = ∆v
/ ∆t
. In this instance, the students of the treatment performed highly significantly
better (ntreat = 151, ncontr = 188) (chapter 6.4.3.2): 39 % gave a correct answer combination referring
to the algebraic sign, compared to 7 % in the control group. 42 % gave a correct answer combination
with regards to the arrows, compared to 9 % in the control group. Arrows corresponding to
velocity were given by only 27 % compared to 62 % in the control group.
The treatment group also showed a more adequate conception of direction in test questions on acceleration
in a two-dimensional motion. In this case, the students were only supposed to give the
direction of acceleration as an arrow, whereas the change in speed was explained in words. In case
of motions along a straight line, no great difference could be observed between treatment group and
control group. With motions along a curved path, however, there were great and highly significant
differences: 77 % of the tested students in the treatment group (ntreat = 35) gave a correct answer on
average, as opposed to only 9 % of the control group (ncontr = 217), resulting in an effect size of d =
2.95 (chapter 6.4.1.2).
Thus the conclusion is drawn that in those classes taught according to this teaching concept, more
students have gained a physically adequate conception of acceleration and have an idea of the direction
of acceleration. This advantage, however, is of no use to them if it comes to interpreting graphs
in motions in one dimension.
In order to test the understanding of Newton’s First and Second Law, problems on motions in one
dimension were used. With problems regarding force, where the answer options were given as texts,
significantly more students, namely 39 % (ntreat = 188), than in the control group (32 %) (ncontr =
211) answered corresponding with the Newtonian conception (chapter 6.5.2.3). Significantly more
students, namely 34 %, than in the control group (21 %) answered problems, where the answer options
were given as time-force graphs, corresponding to the Newtonian conception (chapter 6.5.2.3).
At any rate, with 0.20 and 0.34, respectively, the effect sizes are only weak to medium.
The established FCI test, in which more aspects of the force concept in more variable contexts were
tested with qualitative problems only, yielded a clearly different result. In the post-test, 53 % of the
items were answered correctly (ntreat = 138), in contrast to only 41 % in the traditionally taught control
group (ncontr = 258). This is a significant difference (0.001 scale) with a relatively big effect size
of d = 0.77 (chapter 6.5.1.3). With 31 %, the normalized gain of the students is also significantly
higher (0.001 scale) than in the control group with 18 % (effect size 0.66). The proportion of stu-