Question

If angle of tilt is equal to 10 seconds of arc and length of one division is equal to 2.5 mm in a spirit level then what is radius of tube?

(a) 51.5 m

(b) 51.5 mm

(c) 25.5 m

(d) 25.5 mm

I got this question in an interview.

Asked question is from Spirit Level topic in section Linear Measurements of Engineering Metrology

Answer 1

Correct answer is (a) 51.5 m

Easiest explanation: If radius of tube is R then, arc l is equal to Rα where α is taken in seconds. 1 radian is approximately equal to the 206,265 seconds of arc. 10 sec.  = 0.0000485 radian. Tilt = 2.5 mm/R. By this, R = 51.5 m approximately.