River barges, such as those that run up and down the Mississippi River can—and do—carry an enormous amount of cargo. The power of water’s buoyancy and ability to bear heavy weight are demonstrated in this activity. This activity works great after you’ve watched the Rivers of Life: Mississippi documentary, which shows barge travel along the river (requires a PBS Passport account for free streaming; otherwise, check your local library). If you haven’t watched it, you can explain that cargo such as grain, soybeans, chemicals, road salt, or coal travel up and down the Mississippi River in barges that are sometimes four times the size of a football field.
Materials
174 small objects such as blocks, marbles, or beads that can be carried easily by students.
Shoe box.
Set Up
Divide the small objects into three groups of 58 each. Place one group of 58 objects in the shoe box for easy carrying. The shoe box represents the carrying capacity of a barge. Each object represents 26 tons of coal.
Place two groups of 58 objects—that’s more than 1,500 tons of coal!—and the shoe box (containing the third group of 58 objects) separately at one end of a room.
Each pile represents a different mode of transportation: a barge, a jumbo hopper rail car, and a large semitrailer truck.
If you have three people participating, assign one person to each pile. Otherwise, adapt as is appropriate for your situation.
Activity
The individuals assigned to each pile will carry the objects from one side of the room to the other.
Explain that the barge, rail car, and truck will carry different numbers of objects across the room, based on their real-life carrying capacities. The individual at the pile representing the truck will carry only one object on each trip across the room. The individual who represents the rail car will carry four objects per trip across the room. The individual representing the barge will carry the shoe box containing all 58 objects in one trip. Each person should cross the room as many times as necessary to carry all 58 objects from one end of the room to the other.
Questions
How many times did it take each type of transportation to move all 1,500 tons of coal? (Truck: 58; Rail Car: 15; Barge: 1)
Which type of transportation carried the most? (The barge)
Why might a barge be able to carry so much more weight than a truck or a train? (The buoyant properties of water mean that less energy is needed to move even very heavy objects)
What limitations are there to transporting goods by river? (Not all rivers are large enough for barges; rivers do not go all the places that highways or rails might go; rivers aren’t at all straight, so it might take longer to get from one place to another)
Credit: “Navigation: Traveling the Water Highways; Grade School Edition.” US Geological Survey with other partners.