Y-component of velocity after collision between 0.2 kg and 0.1 kg objects

[tasveerk]

Hello,
I am having some trouble with this question regarding momentum. I have looked around online and I have found the answer but not a decent explanation. If one of you could show me how to answer this I would greatly appreciate it.
Thanks
Two objects of mass 0.2 kg and 0.1 kg, respectively move parallel to the x-axis. The 0.2 kg object overtakes and collides with the 0.1 kg object. Immediately after the collision, the y-component of the velocity of the 0.1 kg is 1 m/s upward. What is the y-component of the velociy of the 0.1 kg object immediately after the collision?

a. 2 m/s
b. .5 m/s downward
c. 0 m/s
d. .5 m/s upward
e. 2 m/s upward

0.2 kg O-------->
---------0.1 kg 0---->

 

[vishal007win]

what is thing that's troubling you?
is answer (B) correct?

 

[cepheid]

To solve this problem, all you have to do is apply the principle of conservation of momentum. Was there any NET momentum in the y-direction before the collision (yes or no)? So what does that tell you about the net momentum in the y-direction after the collision?

 

[tasveerk]

Hello,
The answer is A. I have a feeling I know what is going on, but I just want to see the problem done so I can be sure. I believe the velocities of the two objects are the same at the time of collision so we can rule this out of the initial momentum. Then we can set the initial momentum equal to the final momentum which would be something like (0.2)(1) + (0.1)(V) and then solve for v.

 

[tasveerk]

@cepheid
Does this mean the answer is 0?

 

[cepheid]

@cepheid
Does this mean the answer is 0?

The TOTAL momentum in the y-direction is zero before the collision, agreed? Therefore, by conservation of momentum, the TOTAL momentum in the y-direction must still be zero after the collision, right?

What does this tell you about the momenta of the individual particles in the y-direction after the collision?

 

[tasveerk]

Hello,
I understand the question better now. Thanks everyone.