tmin=dvc=50 10s=5s。
(2) Because the static water velocity is greater than the current velocity, when the combined velocity direction is perpendicular to the river bank, the crossing distance is the shortest. According to the law of parallelogram, there are:
cosθ=vsvc= 12
Therefore, the bow of the assault boat should form an angle θ = 60 with the river bank.
Answer: (1) The shortest time for soldiers to send people ashore is 5s;
(2) If soldiers want to send people ashore through the shortest voyage, the driver of the assault boat should open the bow and make an angle of 60 degrees with the river bank.