在光滑的水平面上有一个物体同时受到两个水平力F1和F2的作用,在第ls内保持静止状态.若两个力F1、F2随时间变化
的图象如图所示,则下列说法正确的是
A.在第2s内,物体做匀加速运动,加速度大小恒定,速度均匀增大 |
B.在第3s内,物体做匀加速运动,加速度的大小逐渐减小,速度逐渐减小 |
C.在第5s内,物体做变加速运动,加速度的大小逐渐减小,速度逐渐增大 |
D.在第6s内.物体的加速度与速度均为零 |
﹣Karl Marx is a great thinker. Do you know ?
﹣In 1818.( )
A.where he was from
B.when he was born
C.how he learned foreign languages
Yuan Longping is a Chinese rice scientist is leading a search to develop "sea rice".( )
A.whoB.whichC.whom
Grandma wants to watch the program legal Report. Please the TV.( )
A.turn offB.turn onC.turn down
Paper﹣making by the Chinese in the Western Han dynasty(朝代).( )
A.is inventedB.invented
C.was invented
﹣I don't know how to use the App Fun Dubbing.
﹣Ask Jimmy for help. He has lots of in doing it.( )
A.experienceB.troubleC.courage