A man of mass 75kg stands on a weighing machine in a lift. Determine the reading of the weighing machine when the lift is moving: 1. Upwards with an acceleration of 2m/s² 2. Downwards with a constant velocity of 1.5m/s 3. Downwards with an acceleration of 2.5m/s²

Explanation:

Given that,

Mass of a man, m = 75 kg

(1) We need to find the reading of the weighing machine when the lift is moving upwards with an acceleration of 2 m/s². When the lift is moving upward, reading of the weighing machine is given by :

R = m(g+a)

R = 75 (9.8+2)

R = 885 N

(2) When the lift is moving downwards with a constant velocity of 1.5m/s. It means that the lift is at rest. So, the reading is :

R = mg

R = 75 (9.8)

R = 735 N

(3) When the lift is moving downwards with an acceleration of 2.5 m/s². In this case,

R = m(g-a)

R = 75 (9.8-2.5)

R = 547.5 N

Hence, this is the required solution.

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