A rigid rod is placed against the wall as shown in the figure. When the velocity at its lower end is \(10\) ms-1 and its base makes an angle \(\alpha=60^\circ\) with horizontal, then the vertical velocity of its end \(\mathrm{B}\) (in ms-1) will be:
1. | \(10\sqrt{3}\) | 2. | \(\frac{10}{\sqrt{3}}\) |
3. | \(5\sqrt{3}\) | 4. | \(\frac{5}{\sqrt{3}}\) |