Identify Given Values: Initial velocity, $u = 20 \text{ m/s}$ (directed downwards). Final velocity, $v = 80 \text{ m/s}$ (directed downwards). Acceleration, $a = g = 10 \text{ m/s}^2$ (directed downwards). Displacement, $s = h$ (height of the tower).

Select Kinematic Equation: Use the equation relating velocities, acceleration, and displacement for uniformly accelerated motion : $v^2 = u^2 + 2as$

Substitute and Solve: $(80)^2 = (20)^2 + 2(10)h$ $6400 = 400 + 20h$ $20h = 6400 - 400$ $20h = 6000$ $h = \frac{6000}{20} = 300 \text{ m}$