【单选题】A 0.140 - kg baseball is dropped and reaches a speed of 1.20 m/s just before it hits the ground. It rebounds with a speed of 1.00 m/s. What is the change of the ball's momentum?
【单选题】坝基由三层水平土层构成,厚度分别为 8m 、 5m 、 7m ,各土层垂直向和水平向的渗透系数分别为: k 1V =0.01 m/s 、 k 1H =0.04 m/s ; k 2V =0.02 m/s 、 k 2H =0.05 m/s ; k 3V =0.03 m/s 、 k 3H =0.09 m/s 。问垂直渗流和水平渗流时的等效渗透系数最接近下列哪个选项的数值?