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I have a question that would probably be easy for you.

If we could put an elevator together with its shaft on a scale and have its motor pull it up, lets say for 50 floors. will the reading on the scale be less while the elevator is traveling?

I'm not talking about fluctuations that will be caused by inertia as it's starting to move, I'm talking about the weight while the elevator is being pulled up steadily.

I tend to think that it will stay the same but on the other hand I also think that the motor at the top pulls it up like a force that uses energy that objects gravity and might make the scale read less while it pulls?

Or maybe because it's slow it will weight the same and if it would've been pulled up "as fast as a rocket" the elevator will be "weightless" for a few seconds?

I didn't study physics but I'm curious.

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2 Answers 2

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I'm talking about the weight while the elevator is being pulled up steadily.

If the elevator is travelling at constant speed in a constant gravitational field, then its weight will stay the same while it's travelling. However, as it moves upward, it is getting further from the centre of the earth. Hence the earth's gravitational attraction is reducing as it travels up. As weight (a force) is the product of mass and gravitational acceleration, it's weight (not its mass) will reduce as it travels up.

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  • $\begingroup$ In most elevators, the cable goes from the roof of the car, up to the lifting motor, down the elevator shaft past the elevator to the basement, and loops back up to the floor of the car. And the downside of the loop includes a counterweight for the car. All the motor sees iis the weight of the passengers...and friction. $\endgroup$
    – DJohnM
    Commented Aug 2, 2020 at 5:05
  • $\begingroup$ You're right @DJohnM, I've removed that part of the answer $\endgroup$
    – hdhondt
    Commented Aug 2, 2020 at 5:47
  • $\begingroup$ Thank you @hdhondt, I was actually taking the elevator and a shaft as an example, so if it was just a model of an elevator and a shaft a foot high sitting on a scale inside a room, it should be the same except the part of getting far from earth's gravity right? the only thing besides that is that there is another answer which says it will weigh more? Thanks. $\endgroup$
    – Ray
    Commented Aug 2, 2020 at 22:56
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    $\begingroup$ If the elevator car is accelerating upwards, that acceleration is added to the gravitational acceleration, hence because f=ma its effective weight is increased. At constant speed only gravity causes weight. $\endgroup$
    – hdhondt
    Commented Aug 2, 2020 at 23:10
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While the elevator is accelerating upward, which means that its speed upward is increasing, the shaft, elevator, motors, pulleys, etc., will weigh more. If the elevator falls with no resistance from the mechanism, the whole assembly will weigh less; but if the elevator's fall is slowed by a braking system the whole assembly will weigh more.

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