# Centripetal combined with Gravitational Force

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1. Apr 29, 2015

### dliangsta

Hi! So I learned Newtons Law of Gravity and used the numbers to calculate that the acceleration due to the attraction between masses is 9.8m/s/s. Hooray! This is what Ive learned is the acceleration due to gravity. However, does the rotation of the earth and the subsequent centrifugal force play any role in decreasing the strength of gravitational force? I naturally think that it would but what I've learned doesn't reflect this. Thanks :)

2. Apr 29, 2015

### Orodruin

Staff Emeritus
Yes. This is why the Earth is not a perfect sphere (modulo local variations such as mountain ranges).

3. Apr 29, 2015

### dliangsta

Thanks again @Orodruin ! So then, does the 9.8m/s/s decrease because of the centrifugal force?

4. Apr 29, 2015

### Orodruin

Staff Emeritus
This depends on what you refer to. For someone rotating with the Earth, this will be the apparent effect. The measured value of g does differ from location to location (although 9.8 m/s^2 is the best approximation with two significant digits everywhere). When I was in high school, the value we were taught was 9.82 m/s^2, because it is what it is here. See also http://en.wikipedia.org/wiki/Gravity_of_Earth