HOC24
Lớp học
Môn học
Chủ đề / Chương
Bài học
Ex2
1 B
2 D
3 B
4 D
5 D
Ex3
1 is singing
2 go
3 likes - like
4 are staying
5 reads
6 is running
7 listens-isn't listening
8 is your father - is - is watching
9 Do they go
10 are
11 doesn't go
12 go - go
13 am writing
14 have - go
15 have
Ex4
2 B
3 A
4 C
5 C
6 A
7 C
8 A
9 C
Ex5
2 A
3 C
Ex6
1 D
2 C
Ex7
1 friendly
2 talkative
3 independent
4 sensitive
5 creative
0 f
1 c
2 h
3 a
4 d
1 Biên độ A = 8 cm
Tần số góc \(3\pi\) rad/s
Chu kì \(T=\dfrac{2\pi}{3\pi}=\dfrac{2}{3}\left(s\right)\)
Tần số \(f=\dfrac{1}{\dfrac{2}{3}}=\dfrac{3}{2}\)
Pha ban đầu \(\varphi=\dfrac{2\pi}{2}=\pi\)(rad)
2. \(x=8cos\left(\dfrac{2\pi}{3}\right)=-4\left(cm\right)\)
3. \(v_{max}=\omega A=3\pi.8=24\pi\)
\(a_{max}=\omega^2A=9\pi^2.8=72\pi^2\)