Theo định luật bảo toàn động lượng: 

\(m_1v_1=\left(m_1+m_2\right)v\)

\(\Rightarrow v=\dfrac{m_1v_1}{m_1+m_2}=\dfrac{10000.6}{10000+100}=6m/s\)

Vậy vận tốc của các xe là 6m/s

a. Trọng lượng của vật:

P = 10.m = 10.20 = 200N

Do sử dụng ròng rọc động nên thiệt 2 lần về đường đi:

h = 2.s = 2.18 = 36m

b. Do dùng rrđ nên lợi 2 lần về lực:

F = \(\dfrac{P}{2}=\dfrac{200}{2}=100N\)

Công thực hiện của ng đó:

A = F.s = 100.36 = 3600J

c) Công suất của ng đó:

P = A/t = \(\dfrac{3600}{90}=40W\)

a) \(W_{t1}=mgh_1\Rightarrow h_1=\dfrac{W_{t1}}{mg}=\dfrac{400}{2.10}=20m\)

\(W_{t2}=mgh_2\Rightarrow h_2=\dfrac{W_{t2}}{mg}=-\dfrac{600}{2.10}=-30m\)

Khoảng cách từ gốc thế năng đến mặt đất là 30m

b) Độ cao vật rơi: 

h = h₁ + h₂ = 20 + 30 = 50m  

c) Công của trọng lực:

A = W_t1 - W_t2 = 400 - ( - 600 ) = 1000J

a) Điện trở đường dây truyền tải:

R = 50.0,2 = 10Ω

Công suất hao phí do tỏa nhiệt trên đường dây:

P_hp = \(\dfrac{P^2.R}{U^2}=\dfrac{5.10^5.10}{20000}=250W\)

b) Để tăng công suất hao phí đi 4 lần thì phải tăng hiệu điện thế:

\(\sqrt{4}=2\) lần

Điểm danh ai mai đi học giống mình nào :)

Let's play soccer!

Trong các chính sách cai trị của nhà Hán, chính sách nào là thâm độc nhất ?

A. Nộp nhiều thứ thuế đặc biệt là thuế sắt, thuế muối

B. Cống nạp các sản vật quý

C. Thực hiện chính sách lao dịch và binh dịch nặng nề

D. Đồng hóa

1. The house has been built in the forest. It doesn’t have electricity.

___The house which has been built in the forest doesn’t have electricity____________

2. Do you know the man? He is coming towards us.

_____________Do you know the man who is coming towards us?______________

3. I sent my parents some postcards. They were not so expensive.

____________I sent my parents some postcards which were not so expensive_________________________________________________

4. I come from a city. The city is located by the sea.

_________I come from a city which is located by the sea____________

5. The soup was so delicious. I had it for lunch.

___The soup that I had for lunch was so delicious___

6. The man is her father. You met him last week.

➔ ___________The man whom you met last week is her father____________________________.

7. Carta has a sister. Her sister’s name is Juma.

➔ ____________Carta has a sister whose nam is Juma___________________________.

8. Show me the new hats. You bought them last night.

➔ __________Show me the new hats which you bought last night_____________________________.

9. Huyen likes the blue T-shirt. My sister is wearing it.

➔ _____________Huyen likes the blue T-shirt which my sister is wearing__________________________.

10. That is a company. It produces ring.

➔ _______That is a company which produces ring________________________________.

11. The children were attracted by the show. It was performed so many.

➔ _____________The children were attracted by the show which was performed so many__________________________.

12. Linda bought a new phone yesterday. I can use it to send and receive message.

➔ __________Linda bought a new phone yesterday which I can use to send and receive message_____________________________.

13. Tet is a festival. Tet often happens in late January or early February.

➔ ________Tet is a festival which often happens in late January or early February_______________________________.

14. My best friend can compose songs. Ly sings folk songs very well.

➔ _______My best friend can compose songs which Ly sings very well________________________________.

15. Cuong is the boy. He is giving my mom a gift.

➔ ______________Cuong is the boy who is giving my mom a gift_________________________.

she broke her leg as she fell off her bike