Acannon fired horizontally at 20 m/s from the top of a cliff lands 80m away. how tall is the cliff

The height of the cliff is, h = 78.4 m

Explanation:

Given,

The horizontal velocity of the projectile, Vx = 20 m/s

The range of the projectile, s = 80 m

The projectile projected from a height is given by the formula

                            S = Vx [Vy + √(Vy² + 2gh)] / g

Therefore,  

                            h = S²g/2Vx²

Substituting the values

                             h = 80² x 9.8/ (2 x 20²)

                                = 78.4 m

Hence, the height of the cliff is, h = 78.4 m