1 người kéo 1 vật khối lượng m = 30kg lên độ cao h = 1,8m bằng 1 mặt phẳng nghiêng dài 9m mất 15s . nếu bỏ qua ma sát thì lực kéo vật là Fk = 40N. hãy tính:

a, công và công suất của người đó .

b, hiệu suất của mặt phẳng nghiêng 

1.“Do you speak English?" Quan asked Lan …………………………………………………………

2."Are you British or American?" Binh said to me …………………………………………………………

3."Is it raining?" Hoang asked his son …………………………………………………………

4. "Have you got a computer?" Quynh asked her brother …………………………………………………………

5. "Can you type?" My mother said to me …………………………………………………………

6. "Did you come by train?" My brother asked me  …………………………………………………………

7. "Have you been to Bristol before?" My boss said to Mai …………………………………………………………

8. "Are you going to the cinema?" he asked me.

He wanted to know.............................................. .....................

9. The teacher asked, "Who speaks English?"

The teacher wanted to know............................................

10. "How do you know that?" she asked me.  She asked me................................................ ...................

11. "Has Caron talked to Kevin?" my friend asked me. 

My friend asked me................................................ ..................

12. "Have you tidied up your room?" the mother asked the twins.

→ The mother asked the twins ..................................................