一道英语物理力学题
A particle P is moving on the x-axis with constant deceleration 2.5 m s^-2.At time t=0,the particle P pass through the origin O,moving in the positive direction of x with speed 15 m s^-1.图是从O点开始（速度为15）,到A点（速度为0）,然后球再返回去.求球返回到O点时的速度.