Seek Time:

Seek time is the time required to move the disk arm to the required track. The seek time is approximated as

                     
where
                                estimated seek time

                                 number of tracks traversed 

                                constant that depends on the disk drive

                                 startup time

Rotational Delay: 

Disk drive generally rotates at 3600 rpm, i.e., to make one revolution it takes around 16.7 ms. Thus on the average, the rotational delay will be 8.3 ms.