     Swings
Rubric
Contributed by: Council of Chief State School Officers (CCSSO/SCASS)
The Item:

Question #1:  Which two swings go back and forth the fastest? What do the fastest two swings have in common? How do the fastest two swings differ from the slowest two swings?

Question #2:  Tell Jodi and Eduardo how to make Jodi's swing go faster. Tell them about the results of your experiment as you give your answer.

Item Description:

This item introduces students to the concept of a pendulum. The materials of the experiment consist of four strings (two short and two long) tied to four washers (two heavy and two light). The physical experiment itself is designed for obvious results: that is, the shorter the string, the faster the swing. The weight of the pendulum bob (the washer) bears no relation to the period of its swing, nor does the amplitude (the arc incidental to the original force exerted in setting the bob in motion).

Most students perform the experiment correctly, observing that the two shorter pendulums swing faster than the two longer pendulums. The questions ask students to interpret their observations and come to the conceptual discovery of the pendulum. Due to the simplicity of the questions, the focus in scoring the test needs to be on students' interpretations.

Question number one attempts to cue the discovery, "Which two swings go back and forth the fastest?" Answer: the shorter two. "What do the fastest two swings have in common?" They are both short. "How do the fastest two swings differ from the slowest two swings?" They are shorter. The conceptual discovery comes in when students questions why they obtained this result. If a student arrives at the conclusion, "the two shorter swings swung faster because they are shorter," the student has made the connection that is the implicit purpose of the question.

Question two asks students to apply the results of the experiment to the model of a tire swing. How can Jodi and Eduardo make their swing go faster? The purpose of the question is to assess the student's ability to apply what they have observed in the experiment to a hypothetical model. The answer, of course, is shorten the rope. The second part of question two asks students to "tell them about the results of your experiment" as they give their answer. Any logical connection the student has made may be expressed here as they apply the experiment to the model to achieve the desired result. Any method of shortening the rope suggested is an acceptable answer. For instance, one student had the idea to tie knots in the rope, which, in effect, does shorten it.

To receive the highest score, a student must have come to the most complex, logical conclusion involved in the question, which is that the weight of the pendulum bob is irrelevant to the speed of the swing. This conclusion is not explicitly asked for in the question, but implied in the use of differing masses of washers.

 Criterion 1: In either question one or two, score one point for noticing that the swings with shorter strings (A and B) went faster, OR if the student correctly identifies the model as a pendulum. Criterion 2: In either question one or two, score one point for a statement of the underlying concept: that shorten-stringed pendulums go faster because they are shorter. Criterion 3: Score one point if, in question two, the student cites the result of the experiment in order to make a clear connection to the model of the tire swing. Criterion 4: One point for coming to the logical conclusion in either question one or two that weight is irrelevant to the speed of the swing.

©1997-2002 SRI International, Center for Technology in Learning. All rights reserved. Terms of Use  