# The Naked Scientists Forum

### Author Topic: How heavy is an object that is free falling through the air?  (Read 4277 times)

#### Thebox

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##### How heavy is an object that is free falling through the air?
« on: 09/04/2015 02:08:06 »
If an object that is falling has a 1kg mass, how heavy is the object whilst in the air?

#### Ethos_

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##### Re: How heavy is an object that is free falling through the air?
« Reply #1 on: 09/04/2015 03:04:45 »
If an object that is falling has a 1kg mass, how heavy is the object whilst in the air?
Weight and mass are two different thing Mr. Box. If your object is free falling, it will have negligible weight but still remain a 1kilogram of mass. You should really start reading a few good physics books.

#### Thebox

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##### Re: How heavy is an object that is free falling through the air?
« Reply #2 on: 09/04/2015 12:02:16 »
If an object that is falling has a 1kg mass, how heavy is the object whilst in the air?
Weight and mass are two different thing Mr. Box. If your object is free falling, it will have negligible weight but still remain a 1kilogram of mass. You should really start reading a few good physics books.

I know mass and weight is different., thank you for the answer,  to confirm my understanding you are saying that a falling object has no weight, it is weightless?

#### evan_au

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##### Re: How heavy is an object that is free falling through the air?
« Reply #3 on: 09/04/2015 12:27:18 »
When objects fall through a vacuum, or at slow speeds through the air, they are weightless.

However, when an object falling in air reaches terminal velocity, a scale inside the object will register the return of weight. Terminal velocity is determined by the shape of the object, its mass, and the density of the air.

And when the object strikes the ground, a scale will momentarily register a weight (force) many times the weight of a 1kg mass at rest.

#### Thebox

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##### Re: How heavy is an object that is free falling through the air?
« Reply #4 on: 09/04/2015 12:40:05 »
When objects fall through a vacuum, or at slow speeds through the air, they are weightless.

However, when an object falling in air reaches terminal velocity, a scale inside the object will register the return of weight. Terminal velocity is determined by the shape of the object, its mass, and the density of the air.

And when the object strikes the ground, a scale will momentarily register a weight (force) many times the weight of a 1kg mass at rest.

a scale inside an object?

Potential mass?

potential weight?

weight is pressure between two surfaces?
« Last Edit: 09/04/2015 12:48:29 by Thebox »

#### evan_au

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##### Re: How heavy is an object that is free falling through the air?
« Reply #5 on: 10/04/2015 12:58:43 »
In the metric system, Mass is measured in kilograms.
• Weight is a Force; in the metric system, Force is measured in Newtons.
• The weight of 1 kg at Earth's surface is sometimes called a "kilograms force", to distinguish it from a kilogram mass. But physicists always use Newtons for force.
• I understand that the Pound is a measure of weight, not of mass.

1 kg mass is not always the same as 1 kg force. For example:

A 1kg object stationary at Earth's surface will apply a force of approximately 9.8 Newtons to a set of bathroom scales. Since most people are not very familiar with Newtons, the scale is calibrated to display 1kg weight.

If a 1kg mass were placed on a set of Earth scales on the Moon, the 1kg mass would apply a force of about 1.6 Newtons to the scales. The scales would (wrongly) indicate a mass of 0.16 kg.

If a 1kg mass and a set of bathroom scales were placed inside the International Space station, they would float next to each other, and the 1kg mass would not apply any force to the scales. It would register 0 Newtons, which it would (wrongly) display as 0kg.

If you dropped a 1kg mass on a set of scales from a high building, they would initially float next to each other, and the 1kg mass would not apply any force to the scales. It would register 0 Newtons.

However, assuming the scales were suitably aerodynamic, and the mass was on top, once the combined unit achieved terminal velocity, the scales would again register 9.8 Newtons, and (correctly) display 1 kg.

A 1kg mass weighs slightly less on a day with high barometric pressure, because the density of the air provides a small "buoyancy" force to the mass. The barometric pressure must be taken into account when doing precise measurements of mass.

#### The Naked Scientists Forum

##### Re: How heavy is an object that is free falling through the air?
« Reply #5 on: 10/04/2015 12:58:43 »