Figure shown to students in a written problem. A small ball moves to the right with a speed v 0 in a weightless, frictionless environment. The ball does not spin. Fixed locations in space, in the plane of the page, are marked with X and labeled A and B.
Figure shown to students in a written problem. A ball collides with a rod in two separate experiments (1 and 2) in a weightless, frictionless environment. The ball and rod are not in contact with any other objects. In both experiments the ball moves with the same initial speed v 0 toward the rod and sticks to it. In experiment 1 the ball hits the rod at its center; in experiment 2 the ball hits the rod near its end. Before the ball hits the rod, the center of the rod is at point A, which is fixed in space, that is, if the rod begins to move, its center may leave point A.
A series of photographs that was shown to students as they worked on the tutorial (Ref. 3), which provided students an opportunity to infer that linear and angular momentum are conserved separately, rather than jointly.
Results from the free small ball problem (Fig. 1) for three sections of introductory physics (N total = 340) before tutorial instruction on angular momentum.
Results from the free small ball problem (Fig. 1) at different stages of instruction.
Results from the linear momentum (p) portion of the ball and rod problem (Fig. 2). Not all categories of response are included.
Results from the angular momentum portion of the ball and rod problem (Fig. 2). Not all response categories are included.
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