Một người tác dụng lên mặt sàn một áp suất 1,7.104 N/m2. Diện tích của bàn chân tiếp xúc với mặt sàn là 0,03 m2. Trọng lượng của người đó là A. 5,1.104 N. B. 5100 N. C. 510 N. D. 51 N.

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Exercise 1: Chia động từ trong ngoặc ở đúng thời 1/ - How long you (learn) ....................English ? - I (learn)..................... - English for 5 years. 2/ - Where is Peter ? - He (be)......... in his room. He (sleep). ............He (sleep) since 2 o'clock. 3/ They (live) .........................here for 20 years now. 4/ Look ! Her eyes are red and wet. She (cry)......................... 5/ The boy is tired. He (run)................. for two hours. 6/ You look tired! Yes I (work)...........................very hard. 7/ Where's the magazine I gave you? What (you do) ............................... with it? 8/ We (have) ........................ the same car for twelve years. 9/ This room was white. Now it is blue. He (paint) ................................. it. 10/ This is the first time I (drive) .......................... a car. Thanks for lending me your car. 11/ These shoes are nice and clean. (you clean) .................................. them? 12/ Sorry I'm late. (you wait) .............................. long? 13/ Somebody (steal) ................................... my keys. They are not on the table. 14/ Mary is still watching TV. She (watch) ................................ TV all day. 15/ Look! Somebody (spill) ............................................ wine on the floor. VII/ Past Perfect (Quá khứ hoàn thành). 1. Form a. Khẳng định : S + had + pp b. Phủ định : S + hadn't + pp c. Nghi vấn : Had + S + pp ? 2. The use * Thời quá khứ hoàn thành diễn tả hành động xảy ra trước một hành động quá khứ hoặc một thời điểm quá khứ khác . Thường đi với after, before, when, by the time (cho tới khi), as soon as ( ngay sau khi) Eg : - After he had done his homework, he went to the cinema. ( Sau khi nó làm xong bài tập, nó đi xem phim.) = Before he went to the cinema, he had done his homework. - When I got there, they had gone home. (Khi mà tôi tới đó, họ đã về nhà rồi.) - When he had sung his song, he sat down. (Khi anh ta hát xong, anh ta ngồi xuống) - By the time we got to the station, the train had already left. ( Cho tới khi chúng tôi tới ga, tàu đã chạy rồi) Exercise : Chia động từ trong ngoặc ở đúng thời 1/ After her husband (get) ....................... home, she started to wash the clothes. 2/ When they reached France, they (visit)........................ 13 countries. 3/ When she (arrive) ...........at his house, she (find).................. that he (leave) a few minutes before. 4/ Before Mr Ron met me, he (do)................................. nothing. 5/ Yesterday I was sorry that I (hurt) ....................................him. 6/ They (tell)..................... her that they (not meet )....................... her before. 7/ When she (realise) .............................her mistakes, she apologised. 8/ When I (meet)............................ my cousin 2 weeks ago, he told me that he just (return) ...............................................from the South. Các bn giúp mik với,thanks nhìu