1. A vertical seawater lock is 4m wide and 2m high. The water level is 2 m above the base of the lock on one side, there being no water on the other side. The mass of the lock is 2.5 t and the coefficient of friction between the lock and the slides is 0.25. Determine the force necessary to raise the lock. (Density of seawater = 1025 kg/m3)