Công để đưa một vật lên cao 5 m bằng mặt phẳng nghiêng là 4,5 kJ. Chiều dài mặt phẳng nghiêng là 2000 cm. a. Xác định khối lượng vật biết hiệu suất mặt phẳng nghiêng là 80%. b. Tính công để thắng lực ma sát và độ lớn lực ma sát đó??

Các câu hỏi liên quan

29. "You should work harder on English pronunciation." Miss Jackson said to Tim. -> Miss Jackson said Tim should........................... 30. "Would you like to drink some coffee?" the manager said to me. -> The manager invited me............................ 31. "Where is my umbrella?" she asked. -> She asked............................................. ...................... 32. "How are you?" Martin asked us. -> Martin asked us................................................ ................... 33. He asked, "Do I have to do it?" -> He asked............................................. ...................... 34. "Where have you been?" the mother asked her daughter. -> The mother asked her daughter.......................................... ......................... 35. "Which dress do you like best?" she asked her boyfriend. -> She asked her boyfriend......................................... .......................... 36. "What are they doing?" she asked. -> She wanted to know.............................................. ..................... 37. "Are you going to the cinema?" he asked me. -> He wanted to know.............................................. ................... 38. The teacher asked, "Who speaks English?" -> The teacher wanted to know.............................................. ..................... 39. "How do you know that?" she asked me. -> She asked me................................................ ................... 40. "Has Caron talked to Kevin?" my friend asked me. -> My friend asked me................................................ ................… 41. "What's the time?" he asked. -> He wanted to know .................................................. . 42. "When will we meet again?" she asked me. -> She asked me .................................................. . 43. "Are you crazy?" she asked him. → She asked him .................................................. . 44. "Where did they live?" he asked. -> He wanted to know .................................................. . 45. "Will you be at the party?" he asked her. -> He asked her .................................................. . 46. "Can you meet me at the station?" she asked me. -> She asked me .................................................. . 47. "Who knows the answer?" the teacher asked. -> The teacher wanted to know .................................................. . 48. "Why don't you help me?" she asked him. -> She wanted to know .................................................. . 49. "Did you see that car?" he asked me. -> He asked me .................................................. . 50. "Have you tidied up your room?" the mother asked the twins. -> The mother asked the twins .................................................. .