cho hai quả cầu giống nhau, quả cầu 1 không mang điện tích , quả cầu 2 mang điện tích dương q. sau đó cho hai quả cầu tiếp cúc và tách chung ra 20 cm thì lực đẩy nhau 1 lực 81.10^-5 a, tính điện tích mỗi quả cầu trước và sau khi tiếp xúc b, sau khi tiếp xúc , đặt chúng trong rượu etyliv có hằng số điện môi 27. tính lực tương tác giữa hai của cầu , biết khoảng cách hai quả cầu không đổi

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For questions 36 -50, read the text below and look carefully at each line. Some of the lines are correct, and some have a word which should not be there. Ha line is correct, put a tick ( ~) by the number. Ha line has a word which should not be there, write the word out There are three examples at the beginning. Hibernation syndrome I don't know about you, but come to the winter months, my body seems to require more sleep than in summer and I'm definitely at my happiest when I'm being curled up in a hedgehog-style ball. "Wanting to sleep more in the winter is not natural and nothing to worry about, unless you are sleeping for more than 12 hours a day," says sleep expert Dr James B Maas. The reason for we feel drowsy has as much to do with our biochemistry as it does so with wanting to sniggle up line a couch potato indoors. ·it's all to do with melatonin," explains Dr Maas, ·a hormone with which is secreted by the brain's pineal gland in response to darkness". They may feel more sleepy, but as many people find getting to sleep in winter is a problem. It's hardly surprising. When lounging around indoors drinking mugs of warming up coffee and snacking on chocolate bars doesn't always prepare you for a good night's rest. H you do have trouble nodding off. Deepak Chopra has tip. ·rry a soothing mix of the sweet and sour essential oils, such as orange, geranium and clove are mixed with almond oil and rubbed it on to your forehead just before bedtime." O: ......... to ........ . 0: ......... .√ ........ . O: ...... being .... . 36: ....................... . 37: ....................... . 38: ....................... . 39: ....................... . 40: ··········.············· 41: ....................... . 42: ....................... . 43: ....................... . 44: ....................... . 45: ....................... . 46: ....................... . 47: ....................... . 48: ....................... . 49: ....................... . 50: ....................... .