(adsbygoogle = window.adsbygoogle || []).push({}); [SOLVED] Elastic Collision - but no Final Velocities given!

1. The problem statement, all variables and given/known data

An object of mass 2.0kg is moving at 4.0 m/s to the right. It collides elastically with an object of mass 1.0kg moving at 12.0 m/s to the left. Calculate the velocities of the objects after the collision.

2. Relevant equations

[tex]m_1=2.0kg v_1 =4.0m/s m_2=1.0kg v_2=-12m/s[/tex]

3. The attempt at a solution

I know the equation for an elastic collision:

[tex]m_1*v_1,i + m_2*v_2,i = m_1*v_1,f + m_2*v_2,f[/tex]

(the i = initial, f = final)

I've been given this challenge problem, and all my samples in the textbook have one of the unknowns given to us ... I'll show you what I mean, when I plug-in:

[tex](2.0kg)(4.0m/s) + (1.0kg)(-12m/s) = (2.0kg)v_1f + (1.0kg)v_2f[/tex]

How can I solve for v1f and v2f if I don't have one of them given to me? In the examples from the book one of those is always given, but not in this challenge problem, so I'm not sure how to go about solving it. I tried a system of equations where I solved for v2f in terms of v1f, but then when I plugged back into the same equation I got 0 (which of course I expected since I need two equations to solve a system of equations) ... I'm really at a loss ... any help?

1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

**Physics Forums | Science Articles, Homework Help, Discussion**

Dismiss Notice

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Homework Help: Elastic Collision - but no Final Velocities given!

**Physics Forums | Science Articles, Homework Help, Discussion**