Gọi M và m là khối lượng súng và đạn, vận tốc đạn lúc thoát khỏi nòng súng. Giả sử động lượng của hệ được bảo toàn. Vận tốc giật lùi của súng khi bắn là

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III. Choose the best answer to complete each of the following sentences. 1. VTV2 and VTV3 are well-known______ channels in Viet Nam. A. foreign B. national C. local D. international 2. He is one of the most famous______ in Viet Nam. You can see him appear on weather forecast every day. A. MCs B. comedians C. newsreaders D. weathermen 3. I need a immediately because I can't turn on your TV without it when Isit on the sofa. A. TV screen B. TV viewer C. remote control D. volume button 4. My father likes watching______ programmes. They have a lot of football matches or boxing competitions. A. sports B. animals C. news D. films 5. The main character in this comedy show looks so________. His motions and actions always make me laugh a lot. A. boring B. clumsy C. skilful D. intelligent 6. I watch The Adventures of Tin Tin on TV___ every Saturday. It's a about a smart boy and his loyal small dog. A. documentary B. cartoon series C. broadcast D. weather forecast 7. I like watching science channels because I can a lot of interesting things about my life. A. discover B. test C. instruct D. compete 8. It's difficult for me to decide to watch between two programmes. They're ____ different channels ____the same time. A. on/ in B. from/ at C. on/ at D. from/ in 9. I can't watch my favourite game sho____my father is watching news at present. A. although B. so C. and D. because 10. He likes watching animals programmes, _he also likes watching comedy shows. A. and B.so C. but D. or 11. The TV schedule today is so boring, I decide to go out with my friends. A, although B. so C. because D. but 12. ____ he's a famous actor, he seems to be very friendly with his fans. A. Although B. So C. Because D. And 13. is dancing in your room? - It's my sister. A. Why B. How C. What D. Who 14. _____ is this documentary on? - About half an hour. A. How far B. How much C. How long D. How often 15. ________ of music do you like? - I like Pop and Rock. A. How many kind B. How kind C. What kind D. What much kind 16. ‘Why are you laughing so hard?’ ‘I am watching a ________. It’s really funny!’ A. drama B. news C. comedy D. romance 17. Did you watch the ________ about the history of India? A. documentary B. sitcom C. news D. game 18. Who wants To Be a Millionaire is a kind of ________. A. music programmes B. game shows A. cartoon B. series C. news D. weather forecast 21. Where is the ________? I’d like to change the channel. A. remote control B. volume button C. TV programme D. schedule 22. Could you turn up the ________ please. I can’t hear that singer very well. A. channel B. programme C. volume D. television 23. Let’s take a look at the weather ________ now! A. forecast B. presentation C. broadcast D. programme 24. Did you see the Prime Minister on the 10 o’clock ________ last night? A. drama B. sitcom C. news D. cartoon 25. Jill Newman was a(n) ________ on News at Ten. A. MC B. newsreader C. host D. interviewer 26. _____are you going to invite to your party next week? A. What B. Who C. Whose D. Where 27. _______did you spend in Hanoi? – One week. A. How many B. How much C. How long D. How often 28. ________is a person who reads a report in the program. A. A weatherman B. A comedian C. A newsreader D. A guest 29. We use a _______ to change the channels from a distance. A. remote control B. TV schedule C. newspaper D. volume button 30. I want to watch the cartoon ________ I turn on the TV. A. but B. so C. although D. because