Of course, I need to add a frictional force also. For the cars, there will be some maximum static frictional force to keep it stationary. After it starts to move, this will be replaced with a constant kinetic friction. Before I start, I have to pick some values for things. I don't know why, but I decided to model this as a small train model. I don't think it really matters too much. Also, I have the coefficient of friction on the driving wheels at 0.
View Iframe URL. That is in slow motion so you can see the different cars moving at different time.
Here is a plot of the position of each car relative to its starting position. In this model, the train just keeps on accelerating. Really, I should put a velocity dependent drag force on the train engine so it looks more realistic. However, there is something pretty cool in the above plot.
Look at the time difference between each car starting. It looks to be evenly spaced out in starting times.
This seems to agree with the sound of a real starting train. This starting train problem is one of those weird things. You begin looking at it and modeling it and then you realize there are all sorts of cool things to explore.
Since I clearly left a lot of unanswered questions on the table, I will let you explore them. But wait! I'm not going to leave you empty handed. Here is my VPython code that I started with. I tried to add comments so you could figure out what is happening, but remember that I am a sloppy coder. I don't always do things the most optimal way and neither should you.
Rhett Allain is an associate professor of physics at Southeastern Louisiana University. He enjoys teaching and talking about physics. You can keep exploring trains by checking out these Wonders! We are undergoing some spring clearing site maintenance and need to temporarily disable the commenting feature.
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Help spread the wonder of families learning together. We sent you SMS, for complete subscription please reply. Follow Twitter Instagram Facebook. How does a train work? When was the steam engine invented? What types of power are used by trains today? Wonder What's Next? Try It Out All aboard!
It's time to explore the following activities with a friend or family member: Where are the nearest train tracks to your house? If you don't already know, find out! Chances are you can find some train tracks not too far away from home. Ask an adult family member or friend to take you on a field trip to a local set of tracks to do some exploring. What kinds of objects can you find along the tracks? If possible, sit at a distance from the tracks and wait for the next train to come through.
Can you identify what kind of train it is and what type of fuel it uses? Want to have some outdoor fun? Grab some pool noodles and make Pool Noodle Train Tracks in your backyard! You can add in some sprinklers and pretend to be a steam engine rolling down the tracks. Have fun! Have you ever gone for a ride on a super-fast modern train? Visit the Discovery website to watch the interesting Maglev Train video to see these sophisticated, technological marvels in action! What do you think it would be like to ride on a maglev train?
Do you think you'd be more likely to experience motion sickness on a maglev train or an old-fashioned steam engine? Did you get it? Test your knowledge. What are you wondering? Wonder Words beach natural rest pile option freight piston vacation amusement distance landscape quickly destination metropolitan comfortably passenger vaporized transferred Take the Wonder Word Challenge.
Join the Discussion. Yeet Oct 27, Immersive Reader lover Oct 14, Oct 22, Thomas the train Sep 28, I noticed that in the video the train was connected to coaches but when it left it was not coupled on choochoo.
Oct 3, Andrew Jun 5, Actually electric trains came before diesels and neither were replaced. Jun 17, Thanks for your input, Andrew!
Luke Barett Apr 1, Lets talk train Nov 7, Plz do a vid about crossing gates and crossing lights. CSX railfanning May 20, I loved the video! May 23, They get the electricity from a third rail, or electrical line, along the track. Transformers transfer the voltage from the lines, and the electrical current drives the motors AC or DC on the wheels. Electrical locomotives are used on subways and many commuter rail systems.
Operators control the train by using the throttle, reversing gear and brake. The throttle controls the speed of the locomotive.
The reversing gear enables the locomotive to back up. The brake allows the locomotive to slow and stop. Regardless of the type, locomotives use air brakes and hand brakes to stop the engine. Air brakes use high-pressure air to drive the brake foot against the wheel. The friction between the brake pad and the wheels slows the wheels' motions. The operator also throttles the engine back to slow the train, like when you take your foot off the gas pedal when stopping your car.
A mechanical hand brake is also used in case the air brakes fail usually when there's insufficient air pressure to drive them. All railroad cars have an undercarriage that contains wheels and a suspension system to buffer the ride.
On each end of the undercarriage, couplers , which are like hooks, connect the cars. The track may also provide electrical power along the third rail, as you'll recall. A railroad track consists of two parallel steel rails set a fixed distance apart, called the gauge. The standard gauge is 4 feet 8. The rails are connected to each other by railroad ties called sleepers in Europe , which may be made of wood or concrete.
The rails are usually bolted to the ties. The ties are set into the loose gravel or ballast. Ballast often consists of loose stones that help transfer the load to the underlying foundation. The ties "float" on the ballast and the weight of the track keeps them stabilized. When rail workers are laying train tracks, they often use a flat-bottom steel rail that resembles the steel I-beam girders of construction.
The rail has a wide base or foot, a narrow web and a head wider than the web, but not as wide as the foot. The weights of the rails vary from 80 to pounds 36 to 73 kilograms per yard depending upon the type of train operating on the tracks and the country. Segments of rail track may connect to one another by bolted plates called fishplates, but most modern rail segments are welded together to provide a smooth ride. Beneath the rails, the track is sometimes cushioned or ballasted.
The foundation may be made of sand or concrete. In many cases, railroad tracks are elevated above the surrounding ground and have drainage systems to remove water. They may also be surrounded by fences to prevent animals and people from wandering on to the tracks. Finally, electrical trains will have either a third power rail or overhanging wires that supply the electricity. Depending upon the topography, some curves may be slightly angled or banked to help the train stay on the track as it negotiates the curve.
At various points along the track, rails may have switches , which can move a train from one track to another. Switches and accompanying track are important for controlling traffic. For example, when two trains are operating on the same track, a switch can allow one train to pull off to a holding track while the other one passes.
A switch also can change a train's direction like moving it from a north-south track to an east-west one. Many railroad stations have switching yards where trains are assembled and moved onto various tracks. Finally, signals along the tracks keep the train operators informed of traffic conditions ahead. Signals control train traffic much like traffic lights control automobile traffic on roads.
Besides signals, many locomotives have radios and computer terminals that monitor traffic conditions using information supplied by signaling centers, which are similar to air traffic control stations. Now that we have the mechanics down, let's see how they fit together to move packages and people.
One popular myth is that the standard train gauge was based on the width of the Roman chariot. This is untrue, especially as the Romans didn't use chariots to transport goods and supplies. The standard train gauge of 4 feet 8. Stephenson had been working with various railways used in British mines and settled on what is now the standard gauge.
Freight railroads carry lots of stuff, but the most common item is coal for electrical power plants 44 percent tonnage and 21 percent revenue. Chemicals, farm products, nonmetallic minerals, mixed shipments and other commodities make up the major categories. In , Class I railroads hauled more than 1. Freight railroads make money based on the weight of freight and the distance traveled.
The industry uses the ton-mile as the basic unit, and Class I railroads carried more than 1. Land grants by the federal government to the railroads in the s allowed the railroads to own the tracks. Furthermore, U. While railroads own some of the thousands of freight cars used, car companies and other shippers actually own most of them. The international leaders in freight railroads are the United States, Russia and China. In contrast to the United States, European railroads are mostly government-owned.
They primarily transport passengers and, to a much lesser degree, freight. However, this setup is changing, and hauling freight is becoming increasingly important. European railways don't make as much money hauling freight as their U.
Their situation seems to be similar to that of U. On the passenger front, however, European railroads are millions of meters ahead, as you'll read about next. Before , U. By the s, the railroads were nearly bankrupt. Congress could either deregulate the railroads or nationalize them. Lawmakers opted for the former. The Staggers Rail Act of gave the railroads the freedom to determine the routes of transportation, set rates for moving freight and streamline procedures for sale of rail lines.
The act did set maximum rates that railroads could charge and procedures to prevent abuses by railroad companies. Since the act was passed, railroads have become more competitive and have increased their revenues and volume of traffic significantly. It seems railroads can be a moneymaker. In , Congress created Amtrak to take over passenger services from the freight railroad companies. It also offers cross-country services. Amtrak operates on tracks owned by host railroads.
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