因为3×8=24(元)24>20,所以,不能.
① I can play the violin. ____ A. Boom—boom!
② Can you hear my drum? ____ B. Zing—zing!
③ Listen! It's Peter's triangle. ____ C. Ding—ding!
④ I like playing the piano. ____ D. Ting—ting!
假设某星球表面上有一倾角为θ=37°的固定斜面,一质量为m=2.0kg的小物块从斜面底端以速度9m/s沿斜面向上运动,小物块运动1.5s时速度恰好为零.已知小物块和斜面间的动摩擦因数为0.25,该星球半径为R=1.2×103km.(sin37°=0.6.cos37°=0.8),试求: