Physics: Force Problem 2, physics homework help

A small metal sphere has a mass of 0.19 g and a charge of -25.0 nC . It is 10 cm directly above an identical sphere with the same charge. This lower sphere is fixed and cannot move.

a) What is the magnitude of the force between the spheres? 

Express your answer to two significant figures and include the appropriate units.

b) If the upper sphere is released, it will begin to fall. What is the magnitude of its initial acceleration?