Precise measurements of physical quantities are a need of science. For example to ascertain the speed of an aircraft, one must have an accurate method to find its positions at closely separated instants of time. This was the actual motivation behind the discovery of radar in World War II. think of different examples in modern science where precise measurements of length, time, mass etc, arc needed. Also, where ever you can, give a quantitative idea of the precision needed.

Explanation

(a) Precise measurements of length are made while finding the thickness of cornea for curing eye problems, another example is measurment of fringe system to Michelson-Morley experiment `(~10^(-6)m)`.
(b) Precise measurement of time are done in cesium clock, and we can use these clocks to measure time taken by an electron to complete an orbit around the nucleus `(10^(-15)s)`.
(c ) Precise measurements of mass is done in measuring the masses of isotopes, mass of an electron, etc. Mass spectrometry is a technique used to measure mass of charged particles.