How to select the motor specification based on our requirement?

1.A Nut(Brass) is travelling through the Screw rod(S.S) at a speed of 2mm/sec through distance of 40mm and static load applied on the nut is 15Kg.

2.The end of the screw rod is coupled with a worm gear(Brass) of 21 teeth with P.C.D of 16.0mm.

3.The worm gear is in mesh with a worm(Brass) of p.c.d-6.0mm which is a single start.

Considering the friction between the nut and Screw rod,load factors(i.e 15 Kg),interial Torque,how do i select the motor for this situation?.

Is there any other factor involved or to be considered?

With Regards

A.Jayaram