1) 1. was written; 2. was planted; 3. was laid; 4. was invented; 5. are cleaned 2) 1. the window was broken. 2. the bridge is being repaired (now). 3. the new museum will be opened next year. 4. the kitchen was painted last weekend. 5. the gallery is visited (by a lot of tourists) every year. 3) 1. will she be invited to the gallery? / where will she be invited? 2. is coffee grown in brazil? / where is coffee grown? 3. was the castle painted? 4. will the prizes be given to the winners next monday? / when will the prizes be given to the winners? / who will the prizes be given? 5. was the hotel build in 2000? / when was the hotel build?
1. correct the errors: 1. this novel was written by dickens.2. this tree was planted by my grandfather.3. the table was laid for four.4. the first telephone was invented by alexander bell.5. the streets are cleaned every day.2. rewrite the sentences in the passive: 1. they broke the window. - the window was broken.2. they are repairing the bridge. - the bridge is being repaired.3. they will open the new museum next year. - the new museum will be opened next year.4. he painted the kitchen last weekend. - the kitchen was painted last weekend5. a lot of tourists visit the gallery every year. - the gallery is visited by lots of tourists every year.3. rewrite the affirmative sentences as questions: 1. she will be invited to the gallery. - where will she be invited? 2. coffee is grown in brazil. - where is cofee grown? 3. the castle was painted. - what was done to the castle? 4. the prizes will be given to the winners next monday. - what will be given to the winners next monday? (when will the prizes be given to the winners? )5. the hotel was built in 2000. - when was the hotel built?
Дано: h=4 м a=8 м E=0,5 лк Найти: I Решение: Закон освещенности E=Icosα/R² I=ER²/cosα R - это гипотенуза треугольника с катетами h и а R²=h²+a²=4²+8²=16+64=80 R=√80=4√5 По определению косинуса cosα=h/R I=ER²/cosα=ER³/h I=0.5·(4√5)³/4≈89.4 (кд) ответ: 89.4 кд
Дано: N=100 (на 1 мм) k=2 λ=740 нм=7.4·10⁻⁷ м Найти: α Решение: Условия интерференционных максимумов дифракционной решётки, наблюдаемых под определёнными углами, имеют вид: dsinα=kλ sinα=kλ/d α=arcsin(kλ/d) Период решетки d=1/N (мм)=0,001/N (м) Окончательно получаем α=arcsin(kλN/0,001) α=arcsin(2·7.4·10⁻⁷·100/0,001)≈8,51⁰ ответ: 8,51⁰
Итак, выводим соотношение искомой высоты из равенства энергий кинетической и потенциальной =) 20h=v*2 пишем стандартные уравнение высоты и скорости: h=v0*t-gt*2/2 =) уравнение 1: h=20t-5t*2
v=v0-gt =) уравнение 2: v=20-10t
соотношение 20h=v*2 используем, заменив там скорость на уравнение 2 получаем: h= 20-20t+5t*2 получившееся уравнение приравниеваем уравнению 1 20t-5t*2=20-20t+5t*2 получаем: 10t*2-40t+20=0 сокращаем до: t*2-4+2=0 находим t=2+-корень из 2, примерно 3,4 сек и 0,6 сек. выбираем 2 - корень из2 так как максимальное время полета тела=2 сек (вычисляем подставив в уравнение кинетической энергии) подставляем в уравнение пути: h=20-20(2-корень из 2)+5(2-кореньиз2)*2 вычиcляем, ответ равен h=10
