A 54 kg man stands on a bathroom scale in an elevator that reads the normal forc

Question

A 54 kg man stands on a bathroom scale in an elevator that reads the normal force (in Newtons) of the man on the scale. Starting from rest at t=0, the elevator starts to accelerate upwards with a constant acceleration, attaining its maximum speed of 2.5 m/s in 0.6 s. Then it stops accelerating and travels with this constant speed of 2.5 m/s for 5.0 s. Later it decelerates as the elevator approaches the correct floor.

What does the scale register before the elevator starts to move?
What does the scale register during the first 0.6 after it starts to move?
What does the scale register while the elevator is traveling at constant speed?

Explanation / Answer

1. scale will show only the normal weight that is mass times acc. due to gravity so weight = 54 * 9.81 = 529.74 N 2. for first 0.6 sec, acceleration = (2.5 - 0)/0.6 = 4.17 m/sec2 so reaction force will be, mass * (g + 4.17) = 54 * (9.81 + 4.17) = 754.92 N 3.at constant speed it will show what it was showing before start as there will be no acceleration of elevator and only acceleration due to gravity will act.so, scale reading = 529.74 N

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