217) The point at which the resultant pressure on an immersed surface acts, is known as

218) A notch is used to measure __________ of liquids.

219) A flow is called sonic, if the Mach number is unity.

220) An error of 1% in measuring head over the crest of the notch (H) will produce an error of __________ in discharge over a triangular notch,

221) A flow through a long pipe at decreasing rate is called __________ uniform flow.