Question

Anya knows the velocity of an object. what else does she need to know in order to find the object’s momentum?

Answer 1

Momentum (P) is a vector quantity which is a result of multiplying the object's velocity (v) to its mass (m). 
 
                                              P = mv

If Anya knows the velocity then, she also needs to know the object's mass. The answer is mass. 

Answer 2

Well,siince the equation is p=mv and she already has the velocity (v) now she just needs the mass (m).