如图所示为小明做“测量平均速度”的实验过程,图中的停表每格为1s(转动未超过一周).下面的相关说法中,正确的是( )
A:下滑的小车作匀速运动
B:小车通过上半程的平均速度是13.3cm/s
C:小车通过全程的平均速度是12cm/s
D:以金属片为参照物,下滑的小车是静止的
甲、乙两台热机,甲的效率比乙的低,其含义是( )
用手将一重为5N的物体全部压入水中,物体排开的水重8N,此时物体受到的浮力为____N,放手后物体将____(填“上浮”或“下沉”),待物体静止时所受浮力为____N.
根据短文内容,用方框中所给词的适当形式填空。
but, favorite, want, about, hamburger, and, like, often, I, visit
Dear Han Mei,
Thank you for your letter. I ____ China very much. And I ____ to go to China with my parents. We want ____ Beijing. I know something ____ China from your letters. ____. I don't know much about Chinese food. Could you tell ____ something about it?I like ____ and fish very much. You tell me you ____ eat rice, vegetables and chicken. And your ____ food is jioazi. What kind of food ____ drink can I have in China? Please tell me.