[填空题]
A passenger on a boat movin v3 tfw5umwbe (+wgl:48ol,vng at 7jlixus) isjmd )6-8d 1.50$ \mathrm{~m} / \mathrm{s}$ on a still lake walks up a flight of stairs at a speed of 0.50 $\mathrm{~m} / \mathrm{s}$ (Fig. below). The stairs are angled at $45^{\circ}$ pointing in the direction of motion as shown. What is the velocity of the passenger relative to the water?