239. The method of finding out the difference in elevation between two points for eliminating the effect of curvature and refraction, is

A. reciprocal levelling

B. precise leveling

C. differential levelling

D. flying levelling.

240. A uniform slope was measured by the method of stepping. If the difference in level between two points is 1.8 m and the slope distance between them is 15 m, the error is approximately equal to

A. cumulative, + 0.11 m

B. compensating, ? 0.11 m

C. cumulative, - 0.11 m

D. none of these.

241. A standard steel tape of length 30 m and cross-section 15 x 1.0 mm was standardised at 25?C and at 30 kg pull. While measuring a base line at the same temperature, the pull applied was 40 kg. If the modulus of elasticity of steel tape is 2.2 x 106 kg/cm2, the correction to be applied is

A. - 0.000909 m

B. + 0.0909 m

C. 0.000909 m

D. none of these.

242. The bearing of AB is 190' and that of CB is 260? 30'.The included angle ABC, is

A. 80' 30'

B. 99? 30'

C. 70? 30'

D. none of these.

243. A dumpy level was set up at mid-point between pegs A and B, 80 m apart and the staff readings were 1.32 and 1.56. When the level was set up at a point 10 m from A on BA produced, the staff readings obtained at A and B were 1.11 and 1.39. The correct staff reading from this set up at B should be

A.1.435

B.1.345

C.1.425

D. none of these.

244. The desired sensitivity of a bubble tube with 2 mm divisions is 30". The radius of the bubble tube should be

A. 13.75 m

B. 3.44 m

C. 1375 m

D. none of these.

245. Offsets are measured with an accuracy of 1 in 40. If the point on the paper from both sources of error (due to angular and measurement errors) is not to exceed 0.05 cm on a scale of 1 cm =20 m, the maximum length of offset should be limited to

A.14.14

B. 28.28 m

C. 200 m

D. none of these.

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