thats centripetal force, ie the force directed towards the centre of the uniform circular motion.
questions regarding this will be when they give you the mass, velocity, force and tell you to work out radius, obviously a little more complicated.
umm....you might know to calculate F<sub>c</sub>=F<sub>G</sub>, where F<sub>G</sub>=Gm<sub>1</sub>m<sub>2</sub>/r<sup>2</sup>