IF YOU watch with a physicist's eye a child playing in a sand pit, you might discover some surprising behaviour. The surface of the sand can,be easily .deformed, while the loose sand can be poured like a liquid. Yet dense sand is so strong that it is possible to drive a car on a beach.Sand also often moves in "bursts", such as when avalanches move down the slope of a,sandpile. Once an avalanche reaches the bottom of the pile, it immediately loses its energy and comes ,to a, complete standstill.
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