The diameter of a cylindrical metal rod is measured using a micrometer screw gauge. The diagram below shows an enlargement of the scale on the micrometer screw gauge when taking the measurement. 40 2 30 0.5mm/rev What is the cross-sectional area of the rod? A 3.81 mm? B 11.4 mm? C 22.8 mm? D 45.6 mm? 3.

Choice B is correct because: Micrometer reading = Main scale reading + Micrometer scale reading Micrometer reading = 3.5 mm + 0.31mm = 3.81 mm [Note: Micrometer scale readings are taken in terms of millimeters(mm)] Cross-sectional area of rod = π x r2 Radius of rod = Diameter of rod / 2 = 3.81/2 = 1.905 mm Cross-sectional area of rod = π x (1.905)2 Cross-sectional area of rod = 11.4 mm2 Choices A, C & D are incorrect because they do not correctly state the cross-sectional area of rod as 11.4 mm2.

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Micrometer Screw Gauge | 2012 - M/J - 9702/12 | Q4