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Tianfu mathematics ninth grade final exam answer
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Instead of copying answers, it is better to put your homework aside and read some popular science books to increase your motivation.

Exploring America's "Death Valley": A Moving Stone

"Death Valley" almost never rains all the year round, and there was a record that the temperature exceeded 40 degrees Celsius for more than 6 weeks in a row. Whenever it rains cats and dogs, mud will appear on the hot ground. There is also a "dead crater".

The notoriety of Death Valley was not made public until 150 years ago. /kloc-in the winter of 0/849, a group of gold diggers going to Jinshan cut across the valley, but lost to the harsh climate here, resulting in piles of white bones in the vast yellow sand. Several people who successfully crossed the valley said "Goodbye Death Valley" when they left here sadly, hence the name.

Stone Road in Death Valley: The traces left by stones running freely on the beach have puzzled scientists for decades. This mystery makes people feel like they are on another planet, which is what surprised Brian Jackson, a scientist at NASA.

In the rest of this month, the lump has traveled hundreds of meters-no one can explain why these stones can move by themselves.

After the rainstorm, the almost flat stone road was filled with water. But this alone still cannot explain the behavior of stone movement.

Traces of rock walking can be described as extending in all directions.

In the past period of time, an expedition composed of 17 scientists and college students, led by NASA researchers, headed for this valley of death composed of salt and sand.

The stones scattered on this desert plain are all ordinary dolomite, and there is nothing special about them. They were stripped from the surrounding mountains.

The researchers measured its orbit according to the satellite navigation system GPS. They also analyzed the soil.

Decades of research on stone tracks: "The conclusion is fascinating-nothing!" . Now a new hypothesis has been put forward.

Last winter, with the approval of national park leaders, Kurt Collert Shika, a NASA researcher, dug a hole under some rocks and buried the sensor. Now we can evaluate the measured values of temperature and humidity: it will really freeze here in March. Unless the ice floes carry rocks?

Researchers are impressed that algae can work with clay, wind, ice and rain.

Every stone controls its own destiny, that is, it runs in different directions.

Why do some stones run in parallel and seem to be interrelated? And why others are moving in the opposite direction. Isn't this wind coming from the same direction? Others will even leave a nearly circular trajectory, just like entering a wind vortex.

Hot, dry and barren: it is very difficult to explore in the desert, and small stones like blades can easily puncture tires. The relentless scorching sun can scorch any living thing on this stone road, which is only 4.5 kilometers long and 2.2 kilometers wide. This is a highland and a flat land surrounded by mountains as high as 3,300 meters.

Some stones go hand in hand, and their curves at the corner are almost parallel. Most rocks go uphill and the rest go downhill. There are also some stones missing from the stone track.

Usually, the shape of stones does not affect their movement. The researchers described that their size, weight and geographical features would not affect them. They drifted at will.

As early as 1948, scientists began to study this mystery, and NASA tried to find a solution for the last time. Scientists learned about these free-flowing chunks and named them: "Kahn", a flaky rock weighing 320 kilograms, which only ran 18 meters a month; Diane is much faster, running 880 meters in the same time.