Q. A mass m moving horizontally (along the x-axis) with velocity v collides and sticks to a mass of 3m moving vertically upward (along the y-axis) with velocity 2v. The final velocity of the combination is
A) (2/3)v î + (1/3)v ĵ
B) (3/2)v î + (1/4)v ĵ
C) (1/4)v î + (3/2)v ĵ
D) (1/3)v î + (2/3)v ĵ
Explanation
[Solution from source] Momentum is conserved in this perfectly inelastic collision: m v î + 3m(2v) ĵ = 4m V⃗. So V⃗ = (v/4) î + (6v/4) ĵ = (1/4)v î + (3/2)v ĵ. Swapping the components, (3/2)v î + (1/4)v ĵ, is the common trap. Answer (3).
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.