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3 Fig. 3.1 shows water flowing at very slow speed over a cliff edge. cliff edge water 15m rocks Fig. 3.1 The water falls 15m onto the rocks below. (a) Show that the velocity of the water when it strikes the rocks is 17 m/s. [4] (b) 30 kg of water flows over the cliff edge every second. Calculate the force exerted by the rocks on the falling water. Ignore any splashing. X GRE = 30 x 10 x15 ........ [3] Mechanicat energy - GPE , KE force = [Total: 7] 4500- 8 + KE KE = 4500 30 x 17 - 510 N