如图所示，一人骑自行车以速度V通过一半圆形的拱桥顶端时，关于人和自行车受力的说法正确的是
A．人和自行车的向心力就是它们受的重力
B．人和自行车的向心力是它们所受重力和支持力的合力，方向指向圆心
C．人和自行车受到重力、支持力、牵引力、摩擦力和向心力的作用
D．人和自行车受到重力、支持力、牵引力、摩擦力和离心力的作用
答案：B
题目分析：向心力不是物体受到的力,它是一个效果力,受力分析时不能分析上,本题中向心力由重力和支持力的合力提供,方向指向圆心,所以B对;
点评：本题难度较小，注意向心力是一个效果力，不是物体受到的力，没有离心力这个力
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| Do you know 1 to make super fruit ice cream? Follow the steps below and you can make your own super fruit ice cream. In 2 a bowl of fruit ice cream, you will need: a cup of yogurt and honey, two cups of milk, two teaspoons of sugar and lemon juice, some apple sauce and cheese, one small watermelon. The procedure(过程）of making super fruit ice cream: ★Step l: Peel the watermelon. 3 . ★Step 2: Heat the milk. Add the sugar 4 it. Cool it. ★Step 3: Pour the yogurt, lemon juice and honey into a bowl. 5 . ★Step 4: Put the apple sauce and cheese into the blender. 6 the blender. ★Step 5: 7 the ingredients from the blender. Pour them into the 8 bowl. Cool them in the fridge. Stir(搅拌)them in and put the watermelon pieces 9 the top. Put them into the fridge 10 for about 3 hours. | ||||
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