Author: Beth Kennedy, Elaine Ulrich, Roberta Gangl, Susan Franz, Chris Bode, Kathie Owens
Source: Science and Children, V. 39 no. 6 March 2002
Students are challenged to ask the question, "What materials will allow me to slide the fastest down the slide?" Allow students to make a prediction and plan a procedure to fairly test the question with polymers.
What should students know as a result of this lesson?
Part A: Pass around some samples of the materials that will be used in the slide investigation. Ask the students to describe the textures of these fabrics (rough or smooth). As a pre-assessment ask students to relate their experiences with slippery, smooth objects, walking on an icy sidewalk, feeling rough objects like sandpaper, etc.
Part B: Take the class to the playground and have volunteer students go down the slide. Ask these students to describe the sensation of sliding and how they think they could slow down or speed up in their movement. Ask if they noticed that not all students slid down at the same rate. What might have caused the differences?
Part C: Tell students that today they are going to develop a fair test to determine the effect of material/fabric on the time it takes to slide down the slide.
Assessment: Monitor the students' answers to the questions and discussion. Before proceeding make sure that they have a descriptive knowledge of friction and some differences between different kinds of materials/fabrics. Make sure that they understand the problem to be tested.
Students will work in teams of 3-4. Assign roles (recorder, timer, materials gatherer, sliders). Remind students of safety procedures.
Then allow students to set up a fair testing procedure. It should be similar to: At the top of the slide, the student will wrap his/her rump and legs with the specified material/fabric.
Students will time the slide, using the starting point of the rump being on the top, and the ending point of when the rump hits the end of the slide. Students will do this for each of the materials/fabrics three times and record the results.
Assessment: Monitor the work of the students. Are they carrying out the procedures safely, recording data, and discussing their findings in their group?
Return to the classroom or have the discussion on the playground. Students report their findings. They should conclude that this experiment tested the speed down an inclined plane in relation to the texture or friction of the fabric (polymer). Students will see that it takes longer for a fabric with a rougher surface or a rubber surface to slide than one with a smooth surface.
Discuss the term 'friction' with the students. Point out that friction slows down motion and that friction can be thought of as 'helpful' and 'not helpful'. Give examples of situations when friction is useful and when it is not.
Assessment: Ask the students to tell you how their experiment was a 'fair' test. Ask the students to draw a picture of a situation where friction occurs. Have students tell you where they think friction is found in the drawing. Monitor their answers for accuracy.
The extension of this lesson will depend on the availability of materials, the ability of the students, and whether or not there is time for another experiment. Have the students design and carry out an experiment to test rolling objects down inclined planes of various heights. For example, make classroom size inclined planes out of boards elevated by piles of books. Ask students how to conduct a 'fair' test to see whether objects get to the bottom of a steep inclined plane faster than they would if they rolled down a shallow inclined plane.
Assessment: Monitor the expressed ideas of the students for evidence of understanding the experimental process. If the experiment is conducted, monitor the work of the students. Be sure that they are carrying out the procedures safely, recording data, and discussing their findings in their groups.
An informal introduction to friction should precede this lesson. Mini-lesson activities of rolling objects down an inclined plane, sliding objects across waxed paper and sand paper, and a discussion of students' experiences of walking across ice/slippery floor should be conducted before this lesson. It is unnecessary to identify the materials used as either polymer/non-polymer or having manmade/natural fibers in the context of this lesson, although it is suggested in the materials list that a good variety of materials from these categories be chosen.
The slide is an inclined plane, one of the six basic simple machines. We usually think of the benefits of an inclined plane related to the ease of using one to move objects from a lower level to a higher one (ex: a ramp). In the slide the movement is essentially from a high level to a low one. The rate of movement is partially determined by the friction of the surface of the slide with the material that it contacts.
Friction is the force exerted when one surface rubs against another surface. The strength of the force of friction depends on the type of surfaces that come together and how hard they push together. Rough surfaces produce more friction than smooth surfaces. The slide is a smooth surface; the smoothness of the clothing worn varies. Some friction between the person and the slide is necessary; too little friction might make for a very scary ride!
The type of material and the arrangement of its fibers make for differing degrees of smoothness. Students in this lesson will make qualitative observations to add to their data about the effectiveness of each fabric in facilitating the sliding process. Little detail about the construction or properties of the materials used will be needed. In other words, it is not necessary to distinguish between natural and man-made polymers for this lesson to be taught.
There are numerous examples of friction as useful or not useful. Here are a few:
Friction is a part of our everyday lives.
Please see assessment suggestions in the procedures.
Grouping Suggestions: Groups of 3 or 4 students.
Pacing/Suggested Time: Two class periods (one for Engagement and Exploration, one for Explanation and Elaboration)