Question

Pick up the most accurate and most precise measurement of – 

(a) 50.00 m, 

(b) 5.00 m, 

(c) 5.00 cm, 

(d) 5.00 mm.

Answer 1

The following table gives the relative error in count of the given measurement:

S.No.	I	ΔI	ΔI/l
(a)	50.00m	0.01m	0.01/50=0.2x10-3
(b)	5.00m	0.01m	0.01/50=0.2x10-2
(c)	5.00cm	0.01cm	0.01/50=0.2x10-2
(d)	5.00mm	0.01mm	0.01/50=0.2x10-2

Clearly measurement (a) is most accurate because the relative error in it is minimum. The fourth measurement i.e., (d) is most precise because it is taken with an instrument having minimum least count among the given measurements.