Asemicircular plate ft in diameter sticks straight down into fresh water along the surface find the force exerted by the water on one side of the plate

You would need to know the diameter of the plate (not in the question). This would tell how much of the plate is in the water. Then you'd need to know the speed of the water current. These two figures would let you calculate the force exerted on the submerged portion of the plate.

The center is basically the heart of it