1. The problem statement, all variables and given/known data You stand on a spring scale at the norh pole and again at the equator. Which scale reading will be lower, and by what percent will it be lower than the higher reading? Assume g has the same value at pole and equator. I have no need for the answer to this question but am looking for an explanation, rather. In the solution, the centripetal force due to the Earth's rotation is pointed outwards (opposite to gravity) and I was wondering why this is? Why not add the centripetal force to the force of gravity instead of subtracting it, and find the weight the scale reads this way? Here is a diagram: http://imgur.com/wz5kuTf So any explanation on why the force of the Earth's rotation is outwards in this case as opposed to towards the centre of the Earth would be great. Thanks!