A stone is thrown from a point O O\,O on horizontal ground with velocity k(5i+j)ms−1k(5\mathbf{i} + \mathbf{j})\text{ms}^{-1}k(5i+j)ms−1, where k k\,k is a constant. The maximum height of the stone above the ground is 5 m.
Find the exact value of kkk.
Find the horizontal distance from O O\,O to the point where the stone returns to the ground.