Из формулы теплового расширения металлического стержня L=L1 * ( 1 + a*t) выразите коэффициент теплового расширения a.

Объясните принцип работы электроскопа  . Поднесите пару предметов были ли предметы которые не приобрели электрический заряд ? 

круговорот воды на земле включает,(и варианты): ответа смену дня и ночи; перемещение облаков воздушными течениями; метеоритные дожди ;смену времён года ;перемещение морских судов.

сформулируйте словами распределительное свойство умножения (а+b)*c=ac+bc

помогите пожалуйста,нужен краткий пересказ текста(что-то можно своими словами,но суть нужно передать)заранее спасибо!!! A SOUND OF THUNDER. The sign on the wall seemed to quaver under the film of sliding warm water. Eckels felt his eyelids blink over his stare, and the sign burned in his memory darkness: TIME SAFARI, INC SAFARIS TO ANY YEAR IN THE PAST. YOU NAME THE ANIMAL. WE TAKE YOU THERE. YOU SHOOT IT. The muscles around his mouth formed a smile as he put his hand slowly out into the air, and in his hand waved a cheque for ten thousand dollars to the man behind the desk. "Does this safari guarantee I come back alive?" "We guarantee nothing," said the official, "except the dinosaurs." He turned "This is Mr Travis, your Safari Guide in the Past. He'll tell you what and where to shoot. If he says no shooting, no shooting. If you disobey instructions, there's another stiff penalty of another thousand dollars, plus government action,upon your return." "Hell and damn," Eckels breathed. "A real Time Machine." He shook his head. "Makes you think. If the election had gone badly yesterday, I might be here now running away from the results. Thank God Keithwon. He'll make a fine President of the United States." "Yes," said the man behind the desk. "We're lucky. If Deutscherhad gotten in, we'd have the worst kind of dictatorship. There's an anti-everythingman for you, a militarist, anti-Christ, anti-human, anti-intellectual.People called us up, you know, joking. Said if Deutscher became President they wanted to go live in 1492.Of course it's not our business to conduct Escapes, but to form Safaris. Anyway, Keith's President now. All you got to worry about now is - " "Shooting my dinosaur," Eckels finished it for him. "A Tyrannosaurus Rex. The Thunder Lizard, the damnest monster in history. --Sign this release. Anything happens to you, we're not responsible.Those dinosaurs are hungry." The Machine slowed; its scream fell to a murmur. The Machine stopped. The sun stopped in the sky. The fog that had enveloped the machine blew away and they were in an old time, a very old time indeed, three hunters and two Safari Heads with their blue metal guns across their knees. "That" - Mr Travis pointed - "is the jungle of sixty million two thousand and fifty-five years before President Keith." He indicated a metal path that struck off the jungle into green wilderness, over steaming swamp, among giant ferns and palms.