¿Desde qué altura debe caer el agua de una presa para golpear la rueda de la turbina a 40 m/s?

Ineed to answer this problem but i lack in knowledge, what should i study to answer this problem? i have never used derivatives in a physics problem so i'm not sure what's happening and i can't find videos explaining.

Diego is trying to lift a piano to the second floor of his house. diego uses a pulley system and gives a big lift to the piano.the piano moves upward, then stops, and then it starts to fall to the ground. which list best describes the forces on the piano in the proper order? positive force → balanced force → negative force negative force → balanced force → positive force positive force → unbalanced force → negative force negative force → unbalanced force → positive force

How did world cup soccer become cool?