To understand:

Effects on weight while travelling in an elevator.

Explaination:

Weight of a body on a surface is actually represented by the normal force acting on it. For example , when you stand on the weighing machine , it records the NORMAL REACTION FORCE.

1st Case (Lift going up):

Let the acceleration of the lift be "a" going upwards. So the object in the lift will experience a pseudo-force downwards.

So, the apparent weight of the object will be greater than the actual weight.

2nd Case (Lift going down):

Let the lift go down with the acceleration "a" , such that the object will experience a pseudo force upwards.

So, the apparent weight is lesser than the actual weight of the object.

Hence, when the lift undergoes free fall (accelerated downwards with "g" ) , the normal reaction becomes zero and the object feels weightless.

HOPE IT HELPS.