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From an inertial frame of reference, explain the apparent weight for a person standing in a lift having zero acceleration.

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1. A passenger inside a lift experiences only two forces:

  • Gravitational force mg directed vertically downwards and
  • normal reaction force N directed vertically upwards, exerted by the floor of the lift.

2. As these forces are oppositely directed, the net force in the downward direction will be F = ma – N.

3. Though the weight of a passenger is the gravitational force acting upon it, the person experiences his weight only due to the normal reaction force N exerted by the floor.

4. A lift has zero acceleration when the lift is at rest or is moving upwards or downwards with constant velocity.

5. Thus, a net force acting on the passenger inside the lift will be,

F = 0 = mg – N

∴ mg = N

Hence, in this case the passenger feels his normal weight mg.

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