Final answer:
No, the lump's momentums do not remain equal in magnitude in a perfectly inelastic collision.
Step-by-step explanation:
In a perfectly inelastic collision, the lump's momentums do not remain equal in magnitude. In a collision, momentum is conserved, meaning the total momentum before the collision is equal to the total momentum after the collision. However, in an inelastic collision, some kinetic energy is lost, and the objects stick together after the collision, resulting in a decrease in the magnitude of the total momentum.