Circular Motion,Uniform motion in Vertical Circles

[Lydia22]

Homework Statement

If the object is at the top, the centripetal force (pointing as
always towards the centre) is down and negative.
● If the object is at the bottom, the centripetal force is pointing up and positive

The Attempt at a Solution

I thought any force towards the center is always positive.Am i wrong?

 

[dikmikkel]

Depends on your coordinate system?

 

[LawrenceC]

It's called a sign convention. You may choose it to be whatever you wish but you must be consistent within each problem.