Artist's rendering of historic rail carUse these links to help you navigate to the different activities on this page:Artist's rendering of historic train

BUILD A STEAM ENGINE

This activity aligns with the following National Science Education Standard:
Content Standard B: Physical Science--Transfer of Energy

The following is a simple exercise that demonstrates how steam can be harnessed to create mechanical energy. (For a more detailed look at how a steam engine operates, refer to On Track with Science: How to Build a Miniature Steam Engine.)

A steam engine converts heat energy into mechanical energy. When water is heated, it becomes water vapor, and its volume increases about 1,600 times. The increased volume of water vapor produces a force that is used to operate a mechanical structure. Such engines once ran most trains, ships, factories, and some cars.

In about A.D. 60, a man named Hero used wood to boil water, and he proceeded to use steam from the boiling water to power an engine. Students can create their own version of Hero's engine by using a small, metal spice can with a press-on metal lid, a nail, a hammer, water, string, a hot plate, and a ring stand. First, near the top of the can, use the hammer and nail to carefully punch two holes on the opposite sides of the can. Pour about 10 mL of water into the can. Next, place the string under the lid and attach the lid to the can so that equal lengths of string come out of each side. Hang the can from a ring stand, making sure that it hangs without twisting. Place the hot plate under the can. Make sure not to touch the can. Ask students to describe what happens after the water begins to boil and produce steam. How would they describe the motion of the can? (The can begins to rotate.)

Artist's rendering of historic train engine

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MASS AFFECTS FRICTION

This activity aligns with the following National Science Education Standard:
Content Standard B: Physical Science--Motions and Forces

Today, trains pull more massive loads than ever before. Although improved design has reduced friction over the years, additional mass continues to increase both the friction on the tracks and the amount of energy required to pull the train. To help students understand how mass affects friction, obtain four textbooks, a one-meter piece of string, and a spring scale. Follow this procedure:

  • Use the spring scale to measure the mass of one book. Record the figure.
  • Tie the string to make a large loop. Place the loop of string inside the front cover of the book. Hook the spring scale to the other end of the loop.
  • Drag the book across a level surface by pulling on the spring scale at a steady speed. Record the force of friction as shown on the spring scale.
  • Use the spring scale to measure the mass of the second book. Add the second book's mass to the first book's mass and record.
  • Next, place the second book on top of the first book and with the spring scale, drag both across a level surface, again recording the force of friction.
  • Repeat the process, adding the third and fourth books.

What happens to the force needed to pull the books as the number of books increases? How does an object's mass affect the force of friction? From a graph of the data, can you predict the force needed to pull more than four books? Can you draw an analogy between books and trains, and the number of locomotives needed to pull more railroad cars?

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SOUND CONDUCTORS

These activities align with the following National Science Education Standards:
Content Standard B: Physical Science--Position and Motion of Object
Content Standard B: Physical Science--Transfer of Energy

In old movies and cartoons, train robbers sometimes place their ear on a railroad track to check for an oncoming train. Students can learn why this method works by exploring how sound travels at different speeds in different media.

Use a metal coat hanger, a one-meter-long piece of string, and a one-meter-long piece of thin gauge copper wire. First, tie the middle of the string around the hook of the hanger. Wrap one end around your left index finger and the other end of the string around your right index finger. Then, gently tap the hanger against a table. Listen for the sound it makes. Next, with the string still wrapped around your fingers, put your fingers in your ears and tap the hanger again. What do you notice about the sound? Repeat steps, this time using the wire. Which is the better conductor, the string or the wire? (The wire is better) Why? (Sound travels faster through the wire than through the string.) For a simpler demonstration, lay your ear on a wooden table as someone taps it. Then rest your head on your arm and listen for the tapping. You can also put a pillow between your ear and the table.

As an extension, research whether certain materials conduct sound better than others. (The speed of sound is dependent on temperature and the medium through which the sound travels. In solids, atoms are usually closer together, which is why solids transmit sound faster than air does.)

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THE DOPPLER EFFECT
A
t one time or another, most people have observed a train's horn getting higher in pitch as it approaches and then lower as it moves away. This phenomena is referred to as the Doppler effect. To people on the train, the horn would seem to have the same pitch at all times. How can two people listening to the same horn hear different notes? (The motion of the train as it moves toward you causes the waves to be emitted closer together.) To demonstrate this phenomenon, have students stand in the center of a hallway. Starting at the end of the hallway, walk toward the students while blowing a whistle or ringing a bell. Continue walking past the students to the other end of the hall. Discuss the change in pitch. (The sound of the bell or whistle becomes higher as the source of the sound comes closer to the student.)

Have students research the practical applications of the Doppler effect. (Most radar depends on the Doppler effect to locate and determine the speed of objects. The police use Doppler radar to identify speeding motorists.) As an extension, invite a local weatherman to discuss how Doppler radar is used to forecast weather, or have a land surveyor talk to the class about how Doppler satellite receivers have been used to determine geographic positions in remote areas.

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HEAT AFFECTS THE TRACKS

This activity aligns with the following National Science Education Standard:
Content Standard B: Physical Science--Transfer of Energy

Periodically, one will read in newspapers about train derailments resulting from the thermal expansion of metal tracks. Ask students if they have ever run hot water over a jar's metal lid because it was too tightly closed to open. Why does this help? (Because the metal expands under the heat of the water, just as train tracks can expand in high temperatures.)

Expansion must be taken into consideration when designing railroads, highways and bridges. Have students research the measures that engineers employ to prevent concrete roads from cracking or buckling, and trains from derailing. (For example, concrete bridges and highways are built with expansion joints to allow for the expansion and contraction of the construction materials.)

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ENERGY CONSERVATION

These activities align with the following National Science Education Standards:
Content Standard B: Physical Science--Motions and Forces
Content Standard B: Physical Science--Transfer of Energy

Studying trains is a good way to study different types of engines and the evolution of energy efficiency through the years. The earliest locomotives, powered by wood and coal, were highly inefficient because much energy was converted into thermal energy that escaped into the atmosphere. An engine is energy efficient when it minimizes the loss of useful energy. Have students learn about the energy sources and workings of different types of train locomotives and answer the following questions:

  • How would friction affect the energy efficiency of a train? (Friction transforms useful energy into thermal energy.)
  • How expensive are the energy sources for different trains? Which is the most expensive? The least? (Electric trains tend to be more expensive than diesel trains. Maglev trains will be cheap to power, but they are expensive to develop and set up.)
  • Is the energy source renewable? (Wood, for example, is a renewable resource;coal is not.)
  • Does the energy source create pollution or involve safety risks? If so, how can these effects be minimized?

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ENERGY TRANSFORMATION
E
nergy can be transformed from one form to another. Forms of energy include electric, radiant, chemical, mechanical, and nuclear energy. Have students create a simple energy flow diagram for different locomotives (steam, diesel, electric, and Maglev). For example, a steam engine burns coal or wood to transform chemical energy into thermal energy. The thermal energy heats water to create steam. The steam creates mechanical energy to move the train.

As an extension, have students create simple toys that use conversion of energy to create motion. They may use wheels, rubber bands, propellers, and dowels. Have students explain the transformations of energy that occur. This would include the energy they use to push or pull the toys, as well as energy released from the unwinding of rubber bands and so on.

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