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Guide Index

Why Are Peppers Hot?

Can You Beat Jet Lag?

How Do Bees Fly?

Why Does Traffic Jam?

Sand to Nuts

Viewer Challenge
in the classroom
TEACHING GUIDES


Life's Little Questions:
Why Does Traffic Jam?


Ever wonder why traffic sometimes piles up for no reason? The Frontiers crew travels to Los Alamos to investigate this question. Physics and high-tech traffic simulations on supercomputers provide the answers. Simulation is used to understand traffic patterns and design more efficient, workable roads. In fact, a project in Oregon is attempting to simulate an entire city and its population.

Curriculum Links
National Science Education Standards
Activity: Modeling Impact Waves
Extensions




CURRICULUM LINKS


COMPUTER
SCIENCE


 

EARTH
SCIENCE


impact craters

PHYSICAL
SCIENCE/PHYSICS


impact waves

TECHNOLOGY


engineering
design




NATIONAL SCIENCE EDUCATION STANDARDS

SCIENCE AS INQUIRY / PHYSICAL SCIENCE
5-8, 9-12: Motions and Forces
EARTH AND SPACE SCIENCE
5-8: Earth in the Solar System
9-12: Origin and Evolution of the Universe
SCIENCE AND TECHNOLOGY
5-8, 9-12: Abilities of Technological Design
SCIENCE IN PERSONAL AND SOCIAL PERSPECTIVES
5-8: Natural Hazards, Science and Technology in Society
9-12: Natural and Human-induced Hazards, Science and Technology in Local, National and Global Challenges
HISTORY AND NATURE OF SCIENCE
5-8 Science as a Human Endeavor, Nature of Science
9-12: Science as a Human Endeavor, Nature of Scientific Knowledge


ACTIVITY: MODELING IMPACT WAVES

As you see in this episode of Frontiers, some traffic jams can be explained by what traffic engineers call a "backward propagating wave." A propagating wave disperses its energy across a medium. As the wave disperses, it continues to spread out. In the traffic example, when one car slows down momentarily, it creates a backward wave that affects the cars behind it.

When scientists want to study events that cannot be duplicated in a laboratory (like a traffic jam), they must create simulations that can be controlled and repeated to discover predictable theories or laws. Computers like those at Los Alamos are used to simulate events from nuclear wars to terrorist attacks and, now, traffic. Scientists also needed to use models and simulations to research their theories about craters on the moon's surface. In this activity you will create a model to simulate the impact of a meteorite on a planet's surface.


MATERIALS
  • flour
  • ruler
  • large glass or foil cake pan
  • several marbles of varying sizes
  • colored powdered tempera or poster paint
Note: You may wish to conduct this activity outdoors.


PROCEDURE
Part 1: Does the size of the meteor make a difference on the impact?
  1. Fill the cake pan with flour and pack it down somewhat.

  2. Dust the surface of the flour with powdered tempera paint.

  3. Predict what you think will happen if you drop a marble into the flour/paint mixture. Write your prediction on a piece of paper.

  4. From a height of 1 meter above the pan, drop a marble into the flour/paint mixture.

  5. Measure the diameter and the depth of the resulting crater.

  6. Repeat steps 4 and 5 with marbles of varying sizes. Which marbles make the larger impact craters? Why?

  7. Design a method for determining the size of waves sent out from the impact.
Part 2: Does the angle of impact make a difference on the crater?

In the early 20th century, it was thought that volcanoes, not meteors, had made the circular craters on the moon. Scientists theorized that by hitting the surface at an angle, meteors would leave an oblong rather than a circular crater. To test their theories, they made models. What do you learn from this miniature moon model?
  1. Use the same pan of flour, again slightly packed and dusted with tempera paint.

  2. This time you'll shoot the marbles at the flour mixture from different angles. Again, make a prediction of the outcome and write it down. Then shoot the marbles at the pan of flour at different angles.

  3. Measure the diameters of the impact craters. What shapes are the impact craters? How do you explain their shapes?
QUESTIONS

  1. Did the impact of the marble in the flour have any consequences other than the impact crater? Why would this be important for scientists to understand?

  2. What type of wave is sent through the flour after the marble collides with the surface?


EXTENSIONS

  • The experiments you performed with the flour simulated the impact of a meteor hitting sand. Create other models to simulate other parts of the earth or planetary objects. Experiment with how a collision sends impact waves through other media (water, slime, clay, a mud mixture, etc.).

  • The next time you're caught in a traffic jam, investigate the causes. Is it an example of a backward propagating wave?

  • You can simulate your own traffic jam at these websites:


ANSWERS

  • Part 2, Step 3: circular; although the object hits at an angle, the crevice made is round.
  • 1. yes; students should observe the flour being blown out and the waves created by the force of the marbles. They'd also be able to estimate the force of the impact.
    2. longitudinal





 

Scientific American Frontiers
Fall 1990 to Spring 2000
Sponsored by GTE Corporation,
now a part of Verizon Communications Inc.