The speed of a boat is \(5\) km/hr in still water. It crosses a river of width \(1\) km along the shortest possible path in \(15\) minutes. The velocity of the river water is:
1. \(3\) km/hr
2. \(4\) km/hr
3. \(5\) km/hr
4. \(2\) km/hr

Two particles are separated by a horizontal distance x as shown in the figure. They are projected at the same time as shown in the figure with different initial speeds. The time after which the horizontal distance between them becomes zero will be:
                     
1.  $\frac{x}{u}$

2.  $\frac{u}{2x}$

3.  $\frac{2u}{x}$

4.  None of the above

The width of the river is \(1\) km. The velocity of the boat is \(5\) km/hr. The boat covered the width of the river with the shortest possible path in \(15\) min. Then the velocity of the river stream is:
1. \(3\) km/hr
2. \(4\) km/hr
3. \(\sqrt{29}\) km/hr
4.  \(\sqrt{41}\) km/hr

Two boys are standing at the ends \(A\) and \(B\) of the ground where \(AB =a.\) The boy at \(B\) starts running in a direction perpendicular to \(AB\) with velocity \(v_1.\) The boy at \(A\) starts running simultaneously with velocity \(v\) and catches the other boy in a time \(t,\) where \(t\) is: