При перемещении заряда по проводнику за 1 с была совершена работа в 100 Дж. Сила тока составила 5 А. Чему равно сопротивление участка?

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Ответ:

hickov2003

10.06.2021 16:32

Высота, на которую может подняться человек примерно 0,385 м

Объяснение:

Лестница длиной 4 м приставлена к идеально гладкой стене под углом 60 °. Максимальная сила трения между лестницей и полом равна 200 Н. На какую высоту вдоль лестницы может подняться человек массой 60 кг перед тем, как лестница начнет скользить. Массой лестницы пренебречь.

m = 60 кг

L = 4 м

g = 10 Н/кг

α = 60°

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h - ? - высота, на которую может подняться человек

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Со стороны пола на лестницу действует горизонтальная сила Fтр и вертикальная реакция, равная силе веса человека, то есть N = mg. Человек поднялся по лестнице на расстояние x.

Высота подъёма h = x · cos α.

В состоянии предельного равновесия лестницы с человеком сумма моментов сил относительно верхней точки опоры лестницы равна нулю.

- N · L · sin α + Fтр · L · cos α + mg · (L - x) sin α = 0

или

- mg · L · sin α + Fтр · L · cos α + mg · L · sin α - mg · x · sin α = 0

откуда

$x = \dfrac{F_{tr}\cdot L}{m\cdot g} \cdot ctg~\alpha$

$h = \dfrac{F_{tr}\cdot L}{m\cdot g} \cdot \dfrac{cos^2\alpha}{sin~\alpha} = \dfrac{200\cdot 4}{60\cdot 10} \cdot \dfrac{0.5^2}{0.5\sqrt{3} } \approx 0.385 ~(m)$

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Ответ:

PETR511

17.03.2020 22:14

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