Question

Two objects of masses 10kg and 20kg have velocities v1 = 20m/s and v2 = 10m/s, on a collison course, as shown below. If 1500J of kinetic energy is lost in the plastic collision and the objects move on a frictionless surface, what is the momentum of the two objects after the plastic collision?

Answer 1

@Callisto

Answer 2

momentum WILL REMAIN conserved.
p=m1v1+m2v2
Make sure you insert the velocities with their signs.

Answer 3

i know it is conserved what to nexr

Answer 4

For a plastic collision,
(m1+m2)Vfinal = m1v1+m2v2
As @Diwakar put it, the signs of v1 and v2 (and Vfinal) are critical.
According to the question, both are moving in the same direction. Double check with the figureb that only you can see.