Momentum and Elastic Collisions: Finding Final Velocity Ratio

[fizics]

Homework Statement

A massless elastic cord (that obeys Hooke’s Law) will break if the tension in the cord exceeds Tmax. One end of the cord is attached to a fixed point, the other is attached to an object of mass 3m. If a second, smaller object of mass m moving at an initial speed v_0 strikes the larger mass and the two stick together, the cord will stretch and break, but the final kinetic energy of the two masses will be zero. If instead the two collide with a perfectly elastic one-dimensional collision, the cord will still break, and the larger mass will move off with a final speed of v_f. All motion occurs on a horizontal, frictionless surface.
Find v_f/v_0

Homework Equations

m1v1=m2v2

The Attempt at a Solution

I always got 1/sqrt(2), which is not the answer.

 

[Andrew Mason]

The Attempt at a Solution

I always got 1/sqrt(2), which is not the answer.

This is not an attempt at a solution. You have to show your work and explain your reasoning.

AM

 

[fizics]

oh,sorry,I know where I was wrong now,a stupid mistake.hehe