Which one of the following pairs does not have the same dimension?

In dimensional analysis, physical quantities are expressed in terms of fundamental dimensions like Mass [M], Length [L], and Time [T] [t1][t2]. Potential and kinetic energy both represent energy with the dimensional formula [ML2T-2] [t4]. Focal length and height are both measurements of length [L] [t2]. Gravitational and frictional forces are both types of force with dimensions [MLT-2] [t5]. However, density and specific gravity differ significantly. Density is mass per unit volume, having dimensions [ML-3] [t2][c3]. In contrast, specific gravity is the ratio of the density of a substance to the density of a reference (usually water), making it a dimensionless quantity [c3]. Since one has dimensions and the other is dimensionless, they do not share the same dimension, making option 2 the correct answer.

Sources

1. [1] https://personalpages.manchester.ac.uk/staff/david.d.apsley/lectures/hydraulics2/t3.pdf
2. [2] Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 2: The Solar System > 2.3. The Sun > p. 23