题干

如图所示,物体的质量大小为3kg,将它置于倾角为37°的粗糙斜面上,受到一个大小恒为10N的外力F作用,且当力F与斜面的夹角θ由0°增大到180°的过程中,物体始终保持静止状态。则在此过程中物体所受的摩擦力大小的变化范围是(g=10m/s2)             (   )

A:8N~28N

B:18N~28N

C:14N~34N

D:18N~34N

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A

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      Held on the second Wednesday of March each year, No Smoking Day helps people across the UK who want to stop smoking. The activity encourages and helps smokers to give up, and publicizes(宣传) the many sources of help offered to people. Each year over a million smokers take part in the day, while about 40,000 actually give up smoking.
      The much-publicized effects of smoking include increased risk (风险) of heart disease, lung cancer and asthma. However, smoking also causes dull skin and wrinkles. The reducedamount of oxygen getting to the skin accelerates (加速)aging, and makes the skin look sallow (病黄色的). And while many smokers believe that cigarettes help them to cope with stress (对付压力), scientific research has shown that worry levels actually go down after giving up smoking.
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    NHS Stop-smoking Centers are all over the UK, providing free services. They have specially trained employees who can advise you on the best way to stop smoking. There are also a number of free national helpline in England, Scotland, Wales, and Northern Ireland, where expert counselors can discuss with you how to give up smoking step by step.