下列火山、地震活动位于环太平洋地震带的是( )
(____) Is it on your desk?
(____) Sure.
(____) Excuse me! Can I use your eraser?
(____) Where is my eraser?
(____) Look! It's under the chair.
(____) No, it isn't.
A、B两球在光滑水平面上沿同一直线向同一方向运动,mA=1kg,mB=2kg,vA=6m/s,vB=2m/s,当A追上B并发生碰撞后,A、B两球速度的可能值是(取两球碰前的运动方向为正)( )