A:−23π
B:π3
C:23π
D:−23π 或 π3
下列运算中,正确的是( )
- Who gets up ______ in your family?
- My mother. She has to cook breakfast for my father and me.
用下列方法制作如图所示的“喷气火箭”:①将气球吹大,并用夹子把口封紧;②从一根吸管上剪取一小段,用胶带把它固定在气球上;③将一根细绳穿过吸管,并水平拉直,作为“喷气火箭”运动的轨道,把封口的夹子松开,气球就会向____(选填“左”或“右”)运动,使气球由静止变为运动的力的施力物体是____,此现象说明力可以改变物体的____.