万能杠是用胶皮制成，（），烫后头发有弹性、光泽。
A.有弹力
B.轻便灵活
C.柔软轻便
D.随意
参考答案：C
Tom is _______ than he used to be. He has quite a few friends now. He is very happy. [ ]
A. outgoing
B. much more outgoing
C. more much outgoing
D. less outgoing
如图所示，在倾角θ=37°的足够长的固定斜面上，有一质量m=1kg的物体，物体与斜面间动摩擦因数μ=0.2。物体受到沿平行于斜面向上的轻细线的拉力F="9.6" N的作用，从静止开始运动，经2s绳子突然断了。求绳断后多长时间物体速度大小为22m/s。（结果保留两位有效数字，已知sin37°=0.6，g取10m/s2）
