Помогите решить Практическую работу по Химии 9КЛАСС

Помогите решить задачки:Цепь постоянного тока со смешанным соединением состоит из четырех резисторов. 

Заданы: 

R1, Ом

R2, Ом

R3, Ом

R4, Ом

U, I, P

20

40

30

5

I=2 A

Определить: 1) эквивалентное сопротивление цепи Rэк; 

2) токи, проходящие через каждый резистор, I1, I2, I3, I4.

Решение задачи проверить, применив первый закон Кирхгофа.

поднимая краном груз наверх скорость вертикального перемещения груза уменьшают с 16 м/с до состояния покоя в течении 8 секунд

Каков модуль ускорения движения груза? a=.....m/2с

Кудв направлено ускорение груза?

горизонтально в сторону крана

вертикально вверх

вертикально вниз

горизонтально в сторону крана

Каким весом обладает груз в этом случае?

Груз находится в состоянии невесомости

груз обладает повышеным весом

груз обладает пониженным весом

груз обладает таким же весом,как в состоянии покоя

1 .When Mark arrived, the Johnsons______dinner, but stopped in order to talk to him. a) were having c) had been having b) had d) was having 2. English is the main foreign language which______within most school systems. a) teach c) teaches b) is taught d) is teaching 3. In India the right hand______for eating. a) used c) is used b) uses d) is being used 4. Although the sun was shining, it was still cold, because it ______hard for two hours. a) had been raining c) had rained b) was raining d) is raining 5. Japan______up of a chain of more than one thousand islands. a) make c) is making b) is made d) makes 6. My colleagues usually______four days a week, and this week they______five days. a) work, work c) are working, are working b) are working, work d) work, are working 7. An area of rainforest the size of Austria______every year. a) is being destroyed c) destroyed b) destroys d) destroying 8. Suddenly he thought that something______of him. a) expected c) is expected b) was expected d) has been expected 9. I have lost my key again. I______things! I lose things too often. a) always lose c) have always lost b) am always losing d) was always losing 10. A lot of jazz festivals______every year in America. a) are held c) are holding b) hold d) held 11. Scotland ______ from London but in many ways it is a separate nation. a) governed c) is governing b) was governed d) is governed 12. The Highlands are home to many rare birds and animals, which______nowhere else in Britain. a) are found c) weren't found b) aren't found d) cannot be found 13. A seat belt______even if you are sitting in the back seat. a) must wear c) must be worn b) wore d) must be wearing 14. All tickets______before we got in the theatre. a) were sold c) are sold b) have sold d) had been sold 15. Students______next Friday. a) will be examined c) are examined b) will examine d) have been examined 16. "A Farewell to Arms"______in 1929. a) was published c) published b) were published d) has published 17. The dinner______by five o'clock tomorrow. a) will be served c) will have been served b) is served d) will serve 18. He______to tidy the garage. a) was helped c) are helped b) were helped d) have helpe