题目

HOW TO GET MORE SLEEPMany studies warn that not having enough sleep may lead to serious health problems, affecting our daily life, work and study. You’ve probably known this for long, yet you still don’t get a full night sleep due to an incredible work schedule. So what can you do to make more time for sleep, and get a better night’s rest overall?• Invest in a better-quality mattress. If you’re sleeping on a years-old, worn-out mattress(床垫), it’s no wonder why you wake up feeling tired in the morning. 【1】 With a new mattress that’s better suited to your sleeping habits, y一物体由静止开始从粗糙斜面上的某点加速下滑到另一点,在此过程中重力对物体做的功等于(   )A.物体动能的增加量B.物体重力势能的减少量与物体克服摩擦力做的功之和C.物体重力势能的减少量和物体动能的增加量以及物体克服摩擦力做的功之和D.物体动能的增加量与物体克服摩擦力做的功之和
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