For a 5400 RPM drive, worst-case rotational latency is one full rotation: 5400/60 = 90 rev/sec, so ~11ms. Average is half that (~5.5ms). If you also need to seek (yes, we'll definitely need to move on both axes in the worst case scenario requested, likely all the time), 2006-era datasheets show average seek around 11-12ms, with full-stroke seeks around 21-22ms. So worst case total access: ~33ms.

Seagate Momentus 5400.3 manual (2005): https://www.seagate.com/support/disc/manuals/ata/100398876a....

Hitachi Travelstar 5K120 (2006):http://www.ggsdata.se/PC/Bilder/hd/5K120.pdf

WD Scorpio (October 2007): https://theretroweb.com/storage/documentation/2879-001121-a1...