Give an example of (a) a physical quantiy which has a unit but no dimensions. (b) a physical quantity which has neither unit no dimensions. (c ) a constant which has a unit. (d) a constant which has no unit.

Explanation

(a) plane angle `theta=L/r"radian"`
its unit is radian but has no dimensions
(b) Strain = `(DeltaL)/L=("Change in length")/("length")`
It has neither unit nor dimensions
`(c)` Gravitational constant (G) =`6.67xx10^(-11)N-m^(2)//kg^(2)`
(d) Reynold's number is a constant which has no unit.