A 60-kg man stands on a spring scale in a lift. At some instant, he finds that the scale reading has changed from 60 kg to 50 kg for a while and then comes back to original mark. What should be concluded? 

The reading of the spring scale is the normal reaction between man and spring scale (Fig.).As the reading is decreasing, it means normal reaction is decreasing. Firstly, the lift must be moving upwards with constant velocity and decelerated to rest.