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

AFMCAFMC 2007Laws of Motion

Solution:

For upward acceleration apparent weight
$=m(g+a)$
If lift suddenly stops during upward motion then apparent weight $=m(g-a)$ because instead of acceleration, we will consider retardation.
In the problem it is given that scale reading initially was $60\, kg$ and due to sudden jerk reading decreases and finally comes back to the original mark ie, $60\, kg$.
So, we can conclude that lift was moving upwards with constant speed and suddenly stops.