Look at it this way.

Take a 100 foot (30m) water tower. Connect two pipes one 1/2" (15mm) one 4" (100mm) to ground level.

The first you will shut off with your thumb. The second you could not close off with your hand no matter how hard you try.

The static pressure is the same in both instances, but the force (thrust) exerted by that pressure is vastly different. 64 times greater in fact. It is the principle on which all hydrolic systems operate.

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