A=F.s <=> A=5000 . 1000=5000000 J = 5000kJ

Một vật dao động điều hòa với phương trình x = 8cosπt (cm). Tốc độ trung bình trong 1/4 chu kì kể từ lúc t₀ = 0 là

A. 10 cm/s

B. 12 cm/s

C. 16 cm/s

D.20 cm/s

Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions from 36 to 42.

In the 1960s, The Beatles were probably the most famous pop group in the whole world. Since then, there have been a great many groups that have achieved enormous fame, so it is perhaps difficult now to imagine how sensational The Beatles were at that time. They were four boys from the north of England and none of them had any training in music, They started by performing and recording songs by black Americans and they had some success with these songs, Then they started writing their own songs and that was when they became really popular. The Beatles changed pop music. They were the first pop group to achieve great success from songs they had written themselves. After that it became common for groups and singers to write their own songs. The Beatles did not have a long career. Their first hit record was in 1963 and they split up in 1970. They stopped doing live performances in 1966 because it had become too dangerous for them - their fans were so excited that they surrounded them and tried to take their clothes as souvenirs! However, today some of their songs remain as famous as they were when they first came out Throughout the world many people can sing part of a Beatles song if you ask them.

What is not true about the Beatles?

A. The members had no training in music

B. They had a long stable career

C. They became famous when they wrote their own songs

D. They were afraid of being hurt by fans

Phương trình z 2 + 2 z + 10 = 0 có hai nghiệm là z 1 ;   z 2 . Giá trị của z 1 - z 2 là

A. 4

B. 3

C. 6

D. 2

Ở gà, giới đực mang cặp nhiễm sắc thể giới tính XX, giới cái mang cặp nhiễm sắc thể giới tính XY. Cho phép lai: Pt/c: gà lông dài, màu đen x gà lông ngắn, màu trắng thu được F1 toàn gà lông dài, màu đen. Cho gà trống F1 giao phối với gà mái chưa biết kiểu gen thu được F2 gồm:

+ Gà mái: 40% lông dài, màu đen: 40% lông ngắn, màu trắng: 10% lông dài, màu trắng: 10% lông ngắn, màu đen.

+ Gà trống: 100% lông dài, màu đen.

Biết một gen quy định một tính trạng trội lặn hoàn toàn, không có đột biến xảy ra. Tính theo lý thuyết, tần số hoán vị gen của gà F1 là

A. 5%.

B. 25%

C. 10%

D. 20%