- #1

Sphere

- 18

- 12

Thank you !

You are using an out of date browser. It may not display this or other websites correctly.

You should upgrade or use an alternative browser.

You should upgrade or use an alternative browser.

- B
- Thread starter Sphere
- Start date

- #1

Sphere

- 18

- 12

Thank you !

- #2

berkeman

Mentor

- 64,441

- 15,790

Please show your calculations and the numbers you used for the Earth's mass, etc. Without seeing your calculations and numbers, I don't think we can be of much help. Thanks.

Thank you !

- #3

Filip Larsen

Gold Member

- 1,650

- 568

- #4

FactChecker

Science Advisor

Homework Helper

Gold Member

- 7,723

- 3,392

That says it is at a latitude of 45 deg. It accounts for the centrifugal acceleration at that latitude. The radius of the Earth (distance to the center of the Earth) is not what you want to use [EDIT] for the calculation of the centrifugal force. You want to find the perpendicular distance to the axis of rotation of the Earth. The shape of the Earth is complicated (see WGS 84 ellipsoid).

You can find a lot of detail on the calculation here: https://en.wikipedia.org/wiki/Theoretical_gravity. It's very complicated and it is no wonder that you are not matching their calculation.

You should be aware that there is some local variation of gravity due to varying densities (and surface altitudes?) that can not be accounted for by simple math models and must be measured locally. There are maps of measured gravity.

Last edited:

- #5

- 10,331

- 11,079

Yes. A careful experimentalist can measure the difference in ##g## over a few meters altitude using only a pendulum. I made a measurement in undergrad labs that was theoretically precise enough to care about my altitude above sea level.(and altitudes?)

In practice, either there is a

- #6

FactChecker

Science Advisor

Homework Helper

Gold Member

- 7,723

- 3,392

I know that there are maps of the gravity at locations on the Earth. I have never used them. I assume that they are accurate for the ground altitude at each location, but I do not know that for sure.Yes. A careful experimentalist can measure the difference in ##g## over a few meters altitude using only a pendulum. I made a measurement in undergrad labs that was theoretically precise enough to care about my altitude above sea level.

- #7

- 24,012

- 15,695

Perhaps that's a measured value. That obviates the need for calculation.With what terrestrial radius did they arrive to calculate this value of 9.80665 m/s2 and why?

Thank you !

- #8

Filip Larsen

Gold Member

- 1,650

- 568

As far as I am aware, it is (now) a defined value with an exact value: https://physics.nist.gov/cgi-bin/cuu/Value?gnPerhaps that's a measured value.

- #9

Klystron

Gold Member

- 1,060

- 1,611

- pendulums,
- dropping ferromagnetic material through electromagnetic fields, and
- laser interferometer.

- #10

Bystander

Science Advisor

Homework Helper

Gold Member

- 5,424

- 1,512

"Station" at NBS/NIST, Boulder, Bldg. 2(?), NW corner in the "back" hallway; may still be there and certified current, or not. This was pre-Sumatra, https://www.jpl.nasa.gov/news/nasa-details-earthquake-effects-on-the-earth .I know that there are maps of the gravity at locations on the Earth. I have never used them. I assume that they are accurate for the ground altitude at each location, but I do not know that for sure.

- #11

Sphere

- 18

- 12

Thanks to everyone !

Share:

- Replies
- 3

- Views
- 1K

- Last Post

- Replies
- 7

- Views
- 829

- Last Post

- Replies
- 1

- Views
- 723

- Replies
- 33

- Views
- 3K

- Last Post

- Replies
- 3

- Views
- 710

- Last Post

- Replies
- 1

- Views
- 653

- Last Post

- Replies
- 2

- Views
- 401

- Replies
- 38

- Views
- 2K

- Last Post

- Replies
- 5

- Views
- 942

- Replies
- 7

- Views
- 1K