# Gravitational field strength at latitude

• zohapmkoftid
In summary, the conversation discusses the differences between mg0 and mgθ, with mg0 being the gravitational force on an object and mgθ being the apparent weight of the object at a specific latitude. The term "apparent gravity" is used interchangeably with gθ, which is also referred to as the local value of g as a function of θ in the textbook being used (New Way PHYSICS for Advanced Level). The author's terminology is reasonable as they are combining the strictly gravitational component with the effect due to rotation. When measuring body weight, the reading on a balance corresponds to mgθ rather than mg0. However, this is a simplified model of the Earth and does not take into account other factors.

#### zohapmkoftid

This figure is captured from my physics textbook and it is about the gravity at latitude

http://pix.gogobox.com.tw/out.php?i=567045_.JPG [Broken]

I want to know the difference between mg0 and mg(theta). Which one is the weight of the object? Thank you!

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Looks to me like mg0 is the gravitational force on the object and mgθ is the apparent weight of the object at latitude θ. The apparent weight is the gravitational force minus the centripetal force. (If you hung an object from a string, the string would end up parallel to the apparent weight.)

Is gθ called 'apparent gravity'?

zohapmkoftid said:
Is gθ called 'apparent gravity'?
That's what I would call it, but it is also called the local value of g as a function of θ. It's somewhat a matter of semantics. What does your textbook call it? (What text are you using?)

It is a Hong Kong textbook called New Way PHYSICS for Advanced Level
In the book, gθ is called gravitational field strength at latitude θ
I think the author uses the wrong name
The gravitational field strength at latitude θ should be g0, right?

Here is the related page from my textbook

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zohapmkoftid said:
I think the author uses the wrong name
The gravitational field strength at latitude θ should be g0, right?
No, the author's terminology is reasonable. When they talk about 'gravitational field strength at latitude θ' they are lumping together the strictly gravitational component (g0) with the effect due to rotation. Think of it as the 'net' or 'apparent' gravitational field strength. (It is a bit confusing, but commonly done.)

gravity = g0
apparent gravity / gravity at latitude = gθ
weight = mg0
apparent weight = mgθ

I hope I don't understand wrongly

So when we measure our body weight, the reading of the balance = mgθ rather than mg0

zohapmkoftid said:
gravity = g0
apparent gravity / gravity at latitude = gθ
weight = mg0
apparent weight = mgθ

I hope I don't understand wrongly

So when we measure our body weight, the reading of the balance = mgθ rather than mg0
Looks good to me. (Of course, this is just a simple model of the Earth as a sphere, ignoring various complications.)

## 1. What is gravitational field strength at latitude?

The gravitational field strength at latitude is a measure of the force of gravity at a certain point on the Earth's surface. It is affected by factors such as the Earth's rotation, shape, and mass distribution.

## 2. How is gravitational field strength at latitude calculated?

The gravitational field strength at latitude can be calculated using the formula g = GM/r², where G is the gravitational constant, M is the mass of the Earth, and r is the distance from the center of the Earth to the point where the gravitational field strength is being measured.

## 3. Does gravitational field strength vary at different latitudes?

Yes, gravitational field strength varies at different latitudes due to the Earth's rotation and shape. At the equator, the Earth's rotation results in a slightly weaker gravitational field compared to the poles.

## 4. How does altitude affect gravitational field strength at latitude?

As altitude increases, the gravitational field strength at a certain latitude decreases. This is because the distance from the center of the Earth increases, resulting in a weaker gravitational pull.

## 5. What is the unit of measurement for gravitational field strength at latitude?

The unit of measurement for gravitational field strength at latitude is meters per second squared (m/s²). This represents the acceleration that a mass would experience due to the force of gravity at a specific latitude.