# Calculating earth gravity by using centripetal acceleration

## Homework Statement

I am asked to calculate the value of gravitational acceleration at earth's surface given the following
Moon's period around the earth - 27 days 8 hours
Moons orbit - 60.1 times the radius of earth (6.38 x 10^6 m)

## Homework Equations

Fc=(4*3.142mR)/T2
which works out to be
g=(4*3.142R)/T2

## The Attempt at a Solution

I am able to get the right answer (9.8 m/s2) IF i convert 27 days to MINUTES instead of proper SECONDS.
so where am i going wrong?

ive tried another method where i didvided the moons speed squared by the orbital radius and i get the same wrong answer
2.76e-3

Last edited: