AP physics problem

Pre-College Issues High School Life
1

<p>I can't get this and its starting to **** me off...it's momentum problem from resnick/halliday. I asked my teacher and he couldn't get it but he didn't really put a good effort in solving it. Anyways here it is:</p>

<p>After a completely inelastic collision, two objects of the same mass and same initial speed move away together at half their initial speed. Find the angle between their velocities.</p>

<p>The answer is 120 degrees, but I can't come up with a solution to get that.</p>

2

<p>m(vcosθ,vsinθ)+m(vcosθ,-vsinθ)=2m(v/2,0)</p>

<p>so 2mvcosθ=2m(v/2)</p>

<p>cosθ=1/2</p>

<p>θ=60 degrees</p>

<p>2θ=120 degrees</p>

<p>My English isn't so well cause I'm not a American student.
Hope you'll understand!</p>