Momentum and Elastic Collisions: Finding Final Velocity Ratio

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In the discussion about momentum and elastic collisions, participants focus on calculating the final velocity ratio (v_f/v_0) after a collision between two masses, 3m and m. The problem involves a massless elastic cord that breaks when tension exceeds Tmax, and emphasizes that the final kinetic energy is zero in a perfectly inelastic collision. For elastic collisions, the larger mass moves with a final speed v_f. One participant initially miscalculated the ratio as 1/sqrt(2) but later recognized their error. The conversation highlights the importance of showing work and reasoning in solving physics problems.
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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.
 
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fizics said:

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
 


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

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