(adsbygoogle = window.adsbygoogle || []).push({}); "A cart of mass m moving at velocity v to the right collides with a stationary cart"

1. "A cart of mass m moving at velocity v to the right collides with a stationary cart of mass 2m on an air track, and the two stick together after collision.

What is their velocity after colliding?"

2. Okay, so this is inelastic collision, right? So KEi ≠KEf

But momentum is conserved.

So:

(m1)(v1i) + (m2)(v2i) = (m1 + m2)(final velocity)

(m)(v) + (2m)(0) = (m + 2m)(final velocity)

(m)(v) = (3m)(vf)

mv/3m = vf

...So wouldn't the 1 of the m's cancel out here, creating v/2m???

3. The answer is really v/3... Somehow. How is this?

How does the answer not even have an m?

How do you get this answer?

Thank you!!! :D

**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: A cart of mass m moving at velocity v to the right collides with a stationary cart

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