如图所示，李欣用手拉着小车静止在倾角为30°的光滑斜面向上匀速运动。已知小车的质量为m，重力加速度为g，绳子对小车的拉力大小为F，斜面对小车的支持力大小为N，则
A．F=
，N=
mg
B．F=mg，N=
C．F=，N=mg
D．F=mg，N=
答案：A
题目分析：分析小车的受力情况可知，受到重力、拉力、支持力的作用，由于小车沿斜面向上做匀速直线运动，因此受力平衡，则
，故选A
点评：本题难度较小，主要是搞清楚小车的匀速直线运动状态，垂直斜面方向和沿斜面方向均受力平衡
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| What does "getting along with your teacher" mean, anyway? "Getting along" means you and your teacher have a relationship that 1 for both of you, and that you both get what you 2 from the relationship. For your teacher, he or she wants to make 3 you are careful, being respectful and polite, and 4 your best to learn. For you, you 5 a teacher who respects you, answers your questions, and tries to 6 you learn. You can get along with your teacher and learn without being friends with him or her, although it's 7 if that happens. In every school, kids say some teachers are too 8 or serious, but don't judge a teacher 9 you are in his or her class and can see for yourself. Most of time, your teacher is on your 10 . And a teacher who's strict may be someone who 11 to do his or her job well-teaching you the 12 you should learn. It's also 13 to remember that making mistakes is a 14 of learning. By pointing out your mistakes and helping you 15 them, a teacher is teaching you. | ||||
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