一根长60cm的细绳，最多能承受100N的拉力，用它吊起一质量为4kg的物体，当物体摆动起来经过最低点时，绳子恰好被拉断．若绳断处距离地面的高度为0.8m，求物体落地时的速度大小．（不计空气阻力，g=10m/s²）

自然界的电、热和磁等现象都是相互联系的，很多物理学家为寻找它们之间的联系做出了贡献。下列说法正确的是（   ）

下列加下划线字的注音全都正确的一项是(    )

阅读短文，掌握大意，然后从A、B、C、D四个选项中，选出可以填入空白处的最佳选项。

    A little sports shop is near my house. It sells (卖) many good things for  1 . At the shop, we can buy soccer balls,  2 , basketballs and so on. Today my  3 and I go to the4  to buy a tennis racket. There are a lot of 5 . And they have different  6   . I think every racket  7  very nice. My sister chooses (选择) a black one, because black is her favorite8  . You know, my sister is a big sports fan. She has a great sports    9   at home-five soccer balls, four basketballs and many tennis balls. She really likes   10  sports.

对社会主义核心价值观的表述正确的是（    ）