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) Angle in a plane in measured in radian, though it has no dimensions.
(b) Strain has neither units nor dimensions.
(c ) Universal gravitational constant (G) has a constant value : `6.67xx10^(-11) Nm^2 kg^(-2).`
(d) Reynold number is a constant which has no units.