Question

Using Models to Answer Questions About Systems

Armando’s class was looking at images of rivers formed by flowing water. Most of the rivers were wide and shallow, but one river was narrow and deep.

Armando’s class thinks that this river is narrow and deep because:

the hill that the water flowed down was very steep, or
the sand grains that the water flowed through were very small.
Armando designed the model below to try to answer the question: Why is this river so narrow and deep?

1a. What features of this model will help Armando answer the question?

1b. How could Armando use this model to test the idea that very steep hills lead to narrow, deep rivers?

1c. How could Armando use this model to test the idea that very small sand grains lead to narrow, deep rivers?

2. Armando thinks that it is the very steep hill that makes this river narrow and deep, but his classmate thinks it is the small size of the sand grains that the water flows through. What results from the model would be evidence that Armando’s idea is correct?

Answer 1

1A: The legs can be a adjusted, as well as the sand can be swapped out. It’s a very good design for running multiple tests.
1B: He could add books or something under the front or back legs in order to increase/decrease the incline, therefore imitating the hypothesis.
1C: He can change out the sand grains to finer ones, or coarser ones, and record his results of each test.
2: If he sets the model at a steep incline and tests it with coarse sand and fine sand, seeing which one makes a narrower, deeper hole.

Answer 2

Stream tables are used for modelling erosion

1 a. The features of the model that will help Armando answer the question

are; The adjustable legs of the stream table, sand and water source.

1 b. To test the idea that very steep hills lead to narrow deep rivers, can

adjust the table legs using a specific sand size and record the results.

1 c. To test the idea that very small sand grains lead to narrow, deep rivers

Armando can try sands of different sizes, with the table legs fixed at a given

location and record the result.

2. The result from the model that would be evidence that Armando's idea is

correct is increase in water path depth with steepness of the stream table.

Reasons:

A river flows due to gravitational forces pulling water from a higher section

to a lower elevation. The speed of flow depends therefore, on the

steepness of the slope over which the river flows.

The energy of the flowing water removes items from the ground such as

sand, granite, and mud as well as water soluble materials such as

limestone as it flows.

Depending on the speed with which the river flows, the river has more

force to remove more materials, and the river flows faster when narrow

than wide, therefore, being able to remove more material, which develops

into a deep and narrow river.

Therefore;

The river is narrow and deep because of the steep hill and the presence of

small sand grains in its path.

1 a. The features in the model that will help Armando answer the question are;

• Elevated water tank (water source)

• The stream table

• The adjustable table legs

• Sand

• Hole for water exit at the lower end of the stream table

1 b. To test the idea that very steep hills lead to narrow, deep rivers, the

depth of the path of water through the sand is measured each time the

adjustable legs are adjusted closer to the lower end of the stream table

increasing the steepness of the table and recording the findings;

$\begin{array}{|c|c|c|}Leg \ position & Width \ of \ water \ path &Depth \ \ of \ water \ path \\1&&\\2&&\\3&&\end{array}$

1 c. Armando can test the idea that very small sand grains lead to narrow,

deep rivers by keeping the leg position fixed and measuring the depth and

width of the water path formed using grades of sand of different sizes.

$\begin{array}{|c|c|c|}Sand \ grade & Width \ of \ water \ path &Depth \ \ of \ water \ path \\1&&\\2&&\\3&&\end{array}$

2 The result from the experiment that would be evidence that Armando's

idea is correct is the result from the tests involving the changing of the

adjustable leg positioning that increasing the steepness of the slope

increases the depth and narrowness of the water path through the sand.

Learn more about stream tables here:

https://brainly.com/question/21549297