The unit of the ratio between thrust and impulse is same as that of

Thrust is a force, and its SI unit is the Newton (N). Impulse is defined as the product of force and the time interval over which it acts, which can be expressed as Newton-seconds (N·s). The ratio of thrust to impulse is therefore N / (N·s), which simplifies to 1/s or s⁻¹. This unit, the reciprocal of a second, is the definition of frequency, which is measured in Hertz (Hz). While speed is measured in m/s [1], wavelength in metres, and acceleration in m/s², only frequency shares the unit of inverse time. Therefore, the unit of the ratio between thrust and impulse is identical to the unit of frequency.

Sources

1. [1] Science-Class VII . NCERT(Revised ed 2025) > Chapter 8: Measurement of Time and Motion > Speed = Total distance covered Total time taken > p. 113