90 km/h : 3.6 = 25 m/s. If you know that on earth g = 9.81 m/s^2, then all you have to do is divide the speed by g. 25/9.81 = 2.548 seconds
At least, if by 'gently rolls off a vertical cliff' means that your starting velocity equals zero.
-- The first thing I do when I wake up is go STRAIGHT to the bathroom. Up to that time, my displacement is equal to distance I traveled from my bed.
-- Once I'm relaxed and back in my room, dithering around and getting dressed, the distance I've traveled since I woke up is growing and growing, but my displacement is staying pretty steady, because I'm still hanging right around my bed.
-- I walk to school, walk between classes, maybe run around the track a couple times, walk to the lunchroom and back to classes, then walk home. By dinner time, my distance traveled during the day might be 3 or 4 MILES, but my displacement is only one floor down from my bedroom to the kitchen.
-- After my homework is done, I slide back into my warm bed and turn out the light. My displacement for the day is now zero ! The straight-line distance from the place I started to the place I finished is zero.
