III-6 Phooling Around in Physics

Exploration

Problem
What observations, predictions and possible hypotheses can you make related to the motion and energies associated with motion along a hot wheels track?

Materials
Hot wheels track with ramps, cars, assortment of spheres, small weights, tape

Procedure
Part A
The illustration below shows the jump ramp set up. Tape the track to the floor or table to minimize motion of the track.

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  1. Find a point of release along the track so a car will just make the jump across the ramps. Mark this point with a piece of tape.

  2. Suppose you were to release a small metal ball from the same spot as above. Predict whether the metal ball will follow the same path as the car, go further or fall short of the ramp. After everyone has made their predictions, try it. Write down your observations.

  3. Try other cars and small spheres, releasing them from various positions along the track. Record your observations.

  4. Try the above tasks without taping the track to the table or floor. Compare the results to earlier trials.

Summing Up
  1. What explanations can you give about the observations made above?

  2. What questions can you ask about the observations?

  3. Design more experiments to test your questions.


Part B
The next illustration shows a loop-the-loop section placed in the track. Again, tape the track to minimize swaying motion.
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  1. Try to release a small metal ball from a point so it just barely travels all the way around the loop without falling away from the track. Mark this point with a piece of tape.

  2. Release a car from the same spot at which you released the ball. Record your observations.

  3. Try releasing several different cars so they just go around the loop. Again record your observations.

  4. What explanations can you give for the observations you made?

  5. What questions do your observations raise?

Summing Up
  1. What explanations can you give for the observations you made in Part B?

  2. What questions do your observations raise?

  3. Design experiments to test your questions.




    Teacher Notes

    III-6 PHOOLING AROUND IN PHYSICS

    Exploration

                   Lab setup        easy         moderate     difficult 
               Calculations     easy         moderate     difficult 
               Reliability      excellent    good         fair 
               Interest         excellent    good         fair 
               Lab time         -1 class     1 class      +1 class 
               Process Skill    A     B     C     D     E     F
               Reasoning        1     2     3     4     5
    Teaching Strategies
    Create as much of an exploratory atmosphere as possible by not communicating any particular results to the students. This is their opportunity to try out some of their notions of potential energy, kinetic energy, rotational energy, friction, etc.

    In Part A, allow the students to work with a minimum of direction. Expect them to apply words like kinetic energy, potential energy and friction. Encourage your students to make careful observations and to raise questions about the physics of the situation.

    In Part B, there may be some transfer of learning from Part A. The students may expect different results for a ball compared to a car going around the loop. Again encourage hypothesizing and questioning about the physics of the situation. You can make loops from single track sections.

    If you have students motivated to organize and conduct some experiments to find answers to some of the questions raised, encourage them to do so. If you can accomplish this, these students are exhibiting the characteristics of real scientist-type students.

    Purchase the materials for these activities at a local toy or hobby store. Or the students may volunteer to bring in some of the cars and track from their own homes. In both parts, attach tape to the track to minimize the transfer of some of the energy of the balls and cars to energy of the moving track.

    Sample Observations/Calculations
    The best results achieved here are the observations students make, questions they ask and possible explanations offered. They may be aware of the transfers of energy from one type to another. They may recognize that some potential energy goes into rotational energy that reduces the linear kinetic energy as a ball rolls down the ramp.

    Summing Up
    1. They should observe that a ball will not jump as far as the car, but will complete the loop from the same release height as the car. The reason is that with a sphere, a significant amount of energy goes into rotational energy. At the bottom of the ramp all the potential energy has transferred into linear transnational and rotational kinetic energy. Therefore, not having as much transnational kinetic energy (speed) it will not jump as far. Ignore the rotational energy of the car's tires because their mass is so small.

    2. Is this observation true of all cars and spheres? What about cars of different masses? What about spheres of different materials? different diameters?

    3. By controlling one variable at a time, they should be able to test their questions. For example, they could test the effect of different sizes of steel balls.

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