Người ta dùng một mặt phẳng nghiêng để kéo một vật có trọng lượng là 500N, lên cao 2m a, Nếu không có ma sát và chiều dài mặt nghiêng là 4m. Tính lực kéo b, Thực tế có ma sát và lực kéo là 280N. Tính hiệu suất của mặt phẳng nghiêng Mn ơi giúp mk nha mk đang cần gấp tí nữa mk thi rồi😥😓😭

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Read the letter and choose the best answer to fill in each blank of the following passage..(10 points) Dear Mai, I’m writing to invite you to a party we ................... (1) at the flat next Friday, December 14th. As you know, ..................(2) is Lan’s 13th birthday next week and my birthday next month, ................... (3) we thought we’d celebrate together and have a joint party. I can’t remember if you know my address or not, but anyway, if you ...............(4) the direction below, you shouldn’t get lost. Take the Number 15 bus from the station and get off ……….. (5) the Star Hotel. Walk down Long Viet Road, past the DanChu Cinema, and then ..................(6) the first turning on the right. That’s LeLoi Road. Turn ............... (7)at the first junction, then go straight past the church as far as the next crossroads. ..............(8) and our flats is the second on the right. Do try and come. Of course you’re ............ (9) to bring someone with you if you want to. Look forward .............................. (10) you then! 1. A. has B. are having C. to have D. having 2. A. it’s B. it C. they’re D. he’s 3. A. too B. but C. because D. so 4. A. to follow B. follow C. following D. follows 5. A. for B. with C. at D. from 6. A. eat B. do C. take D. bring 7. A. left B. ahead C. of D. on 8. A. ahead B. To right C. To turn D. Turn right 9. A. welcomes B. welcome C. welcoming D. to welcome 10. A. to see B. for seeing C. of seeing D. to seeing