I am trying to determine the force required to displace water as shown in the attached picture. My problems here are that I am displacing water using a vertical plunger moving downward at 25cm/sec also as seen in the picture the plunger is at 45degrees. I am confused as to how to calculate the force required to do this Gravity in this case is working to our advantage when the plunger is going downwards and working against us on when the plunger is returning to its original position. What I know: Weight of plunger = 6kgs 125kgs of water of water displaced by plunger at full extension. Distance = 50cm = plunger moves from start position 50cm downwards. Time= 2 sec for plunger to move downward 50cm. 10000kg of water in the tank. Horizontal force of water in tank= 375kg force per unit area = 3678.75 N Can someone give me some insight into how this might be calculated? I dont think its as simple as P=F/a!