(1)滑雪人与滑雪板所受的阻力(包括摩擦和空气阻力)
(2)滑雪板与雪地的动摩擦因素
(1)240N (2)0.5
(1)由 得
由牛顿第二定律得
(2)
—"Excuse me, how can I get to the nearest bus stop?"
—Go down this road. It's about ________ walk [ ]
A. five minute's
B. five minutes'
C. five-minutes
对严重的结节状痤疮有高效的是()
A.异维A酸
B.维A酸
C.阿达帕林
D.过氧苯甲酰
E.壬二酸