1.Let's go out before it starts raining.

2.I'll give you my address after I find somewhere to live.

3.He went to bed after he had done his homework.

4.We'll let you know after we make our decision.

5 I haven't met them since I left school (3 years ago).

6 Robert suddenly began to feel ill while he was doing the examination.

7 Kate will come back home after she finishes the last semester.

Lấy \(g=10m/s^2\)

Thế năng của vật tại điểm bắt đầu rơi \(\left(h_{max}\right)\)

\(W_t=mgh=3.10.30=900\left(J\right)\)

b. Cơ năng của vật tại thời điểm bắt đầu  rơi:

\(W_1=W_t=900\left(J\right)\) (Do lúc này v=0 nên bỏ qua động năng)

Cơ năng của vật tại vị trí cách mặt đất 10m

\(W_2=W_t+W_đ=mgh_2+\dfrac{1}{2}mv^2\)

=\(3.10.10+\dfrac{1}{2}.3.v^2\)

ÁP dụng định luật bảo toàn cơ năng:

\(W_1=W_2\\ < =>300+\dfrac{3}{2}v^2=900\)

Giải PT ta được \(v=20m/s\)

Bài này câu b dùng sự rơi tự do cũng được nhé

Ex2:

1. Walt Disney is one of the most well-known animators in the world.

2. Queen Elizabeth I was known as a very determined and intelligent person.

3. Steve Jobs made a great contribution to the development of technology.

4. Wes Anderson is a master of both live-action and animation filmmaking.

5. His parents were very poor so they had to give him up for adoption.

6. "Sonnet 18" is a famous poem written by William Shakespeare, the father of modern English Literature.

7. Toy Story is the first computer-animated film produced by Pixar Animation Studios.

8. Catherine the Great, who ruled Russia from 1762 to 1796, helped to expand the Russian Empire.

Ex1:

1. The film became a blockbuster, attracting millions of viewers worldwide.

2. Dang Thuy Tram was a/an surgeon who saved lots of people's lives during the resistance war against the US.

3. The establishment of field hospitals during the war provided crucial medical support to injured soldiers.

4. General Vo Nguyen Giap is a famous historical figure of Viet Nam.

5. Steve Jobs died of pancreatic cancer at the age of 56.

6. Walt Disney had a biological daughter and an adopted one.

7. Marie Curie earned two Nobel Prizes, which was an impressive achievement.

8. She was a dedicated person who devoted her life to helping the poor and sick.

9. Elon Musk's companies are known for their cutting-edge technologies and innovations.

10. Her father died when she was a little child, so she had a very difficult childhood.

1. Vietnam was beaten by Thailand as they didn’t play well.
=> If Vietnam had played well, they wouldn’t have been beaten by Thailand.

2.We couldn’t go to school last week because of the flood.
=> If there hadn’t been a flood, we could have gone to school last week.

3. He tried to escape but the police stopped him.
=> The police prevented him from escaping.

4. Couldn’t you find a better hotel?
=> Is this the best hotel you could find?

5. John began playing the piano ten years ago.

=>John has been playing the piano for ten years.

6. She needs to study harder.
=> She doesn’t study hard enough.

7. I only paid a few hundred pounds for the car.
=> The car only cost me a few hundred pounds.

8. He started investigating the case a week ago.
=> He has been investigating the case for a week.

9. I’m quite sure that she didn’t steal the necklace.
=> She can’t have stolen the necklace.

10. The flat’s very noisy but we enjoy living there.
=>Even though the flat’s very noisy, we enjoy living there.

bàn tán gì sôi nổi thế =)))))

Theo đề bài ta có

\(\left\{{}\begin{matrix}p+n+e=58\\p+e=1,9n\end{matrix}\right.\)

Mà \(p=e==>\left\{{}\begin{matrix}2p+n=58\\2p-1,9n=0\end{matrix}\right.\)

Giải HPT ta đc: \(\left\{{}\begin{matrix}p=e=19\left(hạt\right)\\n=20\left(hạt\right)\end{matrix}\right.\)

Tên gọi theo danh pháp IUPAC nhé

Pent-1-in: \(CH_3-CH_2-CH_2-C\equiv CH\)

Pent-2-in:\(CH_3-CH_2-C\equiv CH-CH_3\)

2-Metylbut-1-in: \(\left(CH_3\right)_2CH-CH\equiv CH\)

3-Metylbut-1-in; \(CH_3-CH_2-C\equiv C-CH_3\)

    Thắc mắc gì hỏi mình nhé bn.

1A

2D

3A

4C

5D