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semaf1345789
semaf1345789
08.11.2021 04:40 •  Физика

Укажи, с какой силой давит воздух на поверхность крышки ящика площадью0,39  м2.(принять атмосферное давление за  1013гпа).  ответ  (округли до десятых): воздух давит на поверхность крышки ящика с силой  f≈кн.​

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Ответ:
artyomburyanov
artyomburyanov
15.11.2021 17:01
Fa1=40 мН=0,004 Н
Fа2=36 мН=0,0036 Н

p2=?

Обозначения с индексами: p1 - плотность воды, p2 - плотность масла.

Сила Архимеда равна разнице веса тела в воздухе и в воде, и равна произведению плотности жидкости, ускорения свободного падения и объема тела:

Fa1=P0-P1=p1gV.
Fa2=P0-P1=p2gV.
p2=Fa2/gV.

Нам нужен объем тела, который можно найти через первую силу Архимеда, поскольку нам известна плотность воды:

V=Fa1/p1g=0,004 Н / 1000 кг/м3 / 10 Н/кг=0.0000004 м3.
p2=0,0036 Н / 10 Н/кг / 0.0000004 м3=900 кг/м3.

ответ: плотность масла равна 900 кг/м3.
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Ответ:
1izzka000
1izzka000
14.02.2020 16:35

7 form Reading Test

One Hundred Dollars”

Read the story. Then answer the questions below.

Leonard James is a homeless man. For him, life is always hard. He is always hungry. His shoes have holes in them. He needs a haircut. His clothes are old and dirty. “What I would do with one hundred dollars!” Leonard says. This is a game he likes to play with himself to take his mind off things. He is walking down the street on a Thursday night. The winter air is cold on his face. “If I had one hundred dollars, I could buy new socks,” he says. He continues to walk down the street. “If I had one hundred dollars, I could get a haircut,” he says. He continues to walk down the street. “If I had one hundred dollars, I could buy new pants,” he says. He continues to walk down the street. “If I had one hundred dollars, I could get a hamburger,” he says. His stomach rumbles at the thought. “If I had….” Leonard looks down at the sidewalk. He cannot believe what he sees! Someone has lost his wallet. Leonard picks it up. Inside are five twenty-dollar bills. “One hundred dollars!” Leonard says. He is very excited. “Now I can buy everything I want!” Then Leonard begins to think. “But this is not my money,” he says. Leonard goes to the police station. He gives a police officer the wallet and money. “Thank you,” says the police officer. “You are a very honest man.” Leonard smiles. He turns around and begins to leave the police station. “Hold on,” the police officer says. He reaches in his own pocket and gives Leonard ten dollars. “Get yourself something to eat.”

Questions:

1) What is life like for Leonard?

A. It is hard.

B. It is easy.

C. It is warm.

D. It is full of good food.

2) How does the reader know that Leonard is poor? I. He finds a wallet. II. He has no home. III. He is always hungry.

A. I only

B. I and II

C. II and III

D. I, II, and III

3) Why does Leonard think about what he would do with a hundred dollars?

A. It helps him go to sleep.

B. It takes his mind off things.

C. The police officer asks him to.

D. He knows he will find the money.

4) What time of year is it?

A. spring

B. summer

C. fall

D. winter

5) What does Leonard say he would do with a hundred dollars? I. get a haircut II. buy new clothes III. get a hotel room

A. I only

B. I and II

C. II and III

D. I, II, and III

6) Why does Leonard's stomach rumble?

A. because he is hungry

B. because he is tired

C. because his clothes are dirty

D. because he is homeless

7) “He cannot believe what he sees.” What is another way to write this sentence?

A. He thinks what he sees is crazy.

B. He feels what he sees is good luck.

C. He thinks what he sees cannot be true.

D. He thinks what he sees is scary.

8) Why does Leonard go to the police station?

A. because he owes money

B. because he wants a reward

C. because the wallet is not his

D. because he has committed a crime

Questions (continued):

9) What kind of man does Leonard seem to be?

A. bad

B. dumb

C. good

D. old

10) As used at the end of the story, what does it mean to be honest?

A. to feel good

B. to want more

C. to be truthful

D. to be hopeful

11) How does Leonard seem to feel about what he has done?

A. angry

B. happy

C. sad

D. unsure

12) What does the police officer give Leonard?

A. advice

B. a handshake

C. money to eat

D. the one hundred dollars

13) What kind of man does the police officer seem to be?

A. angry

B. busy

C. kind

D. mean

14) Why does the police officer give Leonard ten dollars?

A. to surprise Leonard

B. so Leonard feels better about returning the wallet

C. because it is part of his job

D. because he wants to get Leonard off the streetsВітаємо в буфері обміну Gboard. Скопійований текст зберігатиметься тут.

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