题干

如图是运动员顶足球时的情景,忽略空气阻力,下列说法正确的是(  )

A:球被顶出,说明力可以改变物体的运动状态

B:顶出去的球在上升过程中,受到平衡力的作用

C:球在上升过程中,重力势能增加,机械能保持不变

D:顶出去的球最终落地,是由于球具有惯性

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答案(点此获取答案解析)

A,C

同类题5

根据短文理解,选择正确答案。

    My parents moved to Mississippi when my brother and I were small children, and we were separated from our Oklahoma grandparents by some 600 miles. This long distance allowed us to only visit our grandparents once a year, either at Christmas or during summer vacation.

    Most of my classmates lived near their grandparents, and I would often hear stories of big families regularly spending time with one another, fishing at “grandpa's” house or going over to “grandma's”for her famous fried chicken. We were disappointed that we did not get to spend more time with our grandparents, but our love for them remained deep and strong.

    We always expected a road trip to Oklahoma. We would count the days, and when the day came, the entire family would pile into our car at four o'clock in the morning. Crossing the Mississippi River into Louisiana, the scenery changed. Crossing the Red River in Oklahoma, we were in a foreign world.

    Every trip to see my grandparents can't be without bringing delight. We jumped out of the car in their driveway to be met with bear hugs. My grandparents wanted to know everything about their grandchildren, and we would sit for hours and tell story after story. Grandma had a meal planned, and you could guess she prepared her grandsons' favorite foods. Of course the best part of the visit was that we were able to do whatever we wanted without punishment from our grandparents. Grandma and Grandpa always had presents for us, short trips planned and lovely surprises, such as the time we got to a local restaurant and ate the world's largest hamburger.