Let h = the distance from the edge of the wall to the water surface (m).
Use g = 9.8 m/s² and neglect air resistance.
The initial vertical velocity of the pebble is zero. Because the pebble hits the surface of the water after 1.5 s, therefore h = (1/2)*(9.8 m/s²)*(1.5 s)² = 11.025 m
<span>The water is held behind a dam, forming reservoir. The force of the water being released from the reservoir through the dam spins the blades of a giant turbine.</span>