题干

 如图所示,一小钢球从光滑固定斜面的a点由静止释放,相继经过b、c两点,ab=bc,则下列判断正确的是(忽略空气阻力的影响)(  )

A:小钢球下滑过程中惯性越来越大

B:小钢球在ab、bc两端内运动的平均速度相等

C:小钢球在ab段重力势能的减少量与bc段动能的增加量相等

D:就a、b、c三点而言,小钢球在a点具有的机械能最大

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答案(点此获取答案解析)

C

同类题4

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    Mick Polly,an owner of a toy store,lives with his teenage daughter Carolina in Kentucky.He is known as the Bike Man.Over the past five years,Mick has built hundreds of bikes for needy kids.

    One day in 2012,a 13﹣year﹣old boy with a broken bike walked by Mick's house."I was working in my garage(车库),and he asked if I could fix it,"says Mick,now 53.

    The boy's bike had a broken wheel.Mick sent a post(帖子) on Facebook,asking his friends if they had the needed part.One friend saw the post and gave away two used bikes.Mick took parts from each to build a new set of wheels for the boy.

    Soon after,Mick repaired a bike for the boy's brother and fixed one for his sister.Word spread,and during the year,he had fixed up lots of bikes for local kids whose parents were not able to afford new ones

    "People are throwing away bikes day and night,"says Mick.

    Mick puts the bikes and bike parts in his garage."I take off the good tires or the handlebars or the seats and use them,"he says.

    Up to now,the bike man has repaired hundreds of bikes and given away nearly 700newly repaired bikes.They're free,but the kids must agree to two things:They have to learn how to put waste things to good use and they have to try their best to study in school.

    If a kid's grades are low,Mick requires a teacher's note"saying that you're doing your best,"Mick says.Mick also hopes the bikes will get kids off the sofa."When I was growing up,we all rode our bikes,"he says."Hopefully these kids can get some exercise."