Aball is thrown straight up with a speed of 3\frac{m}{s}, and it hits the ground with a speed of 15\frac{m}{s}. how tall is the tower? ignore air resistance, and answer in meters.

Explanation:

We have equation of motion v² = u² + 2as

Initial velocity, u = 3 m/s  upwards

Acceleration, a = -9.81 m/s²  downwards

Final velocity, v = -15 m/s  downwards

Substituting  

v² = u² + 2as

(-15)² = 3² + 2 x -9.81 x s

s = -11 m  that is downward

Form the initial position it travels 11 meter downward.

Height of tower is 11 meters

see earlier