Question

A man of mass 50 kg is standing in a lift. Find the apparent weight of man when the lift is (i)

stationary (ii) moving up with an acceleration of 2 m/s2

(iii) moving down with an acceleration

of 2 m/s2

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Answer 1

Solution :

As per the given data ,

• Mass of the man = 50 kg

(i)  stationary

As the lift is stationary the acceleration of the lift will be zero

Hence, the normal force acting on the man will be equal to it's weight

⇒ N = mg

⇒ N = 50 x 10

⇒ N = 500 N

The apparent weight of the man is 500 N when the lift is stationary

(ii) Moving up with a = 2m/s²

First let us draw all the forces acting on the man.

Now equate the forces

⇒ N + ma = mg

⇒ N = mg - ma

⇒ N = m (g - a )

⇒ N = 50 ( 10 - 2 )

⇒ N = 50 x 8

⇒ N = 400 N

The apparent weight of the man when the lift is moving upwards with a 2 m/s ² is 400 N

(iii) Moving up with a = 2m/s²

First let us draw all the forces acting on the man.

Now equate the forces

⇒ N  = mg + ma

⇒ N = m (g + a )

⇒ N = 50 ( 10 + 2 )

⇒ N = 50 x 12

⇒ N = 600 N

The apparent weight of the man when the lift is moving downwards with a 2 m/s ² is 600 N