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# Direction of Particles M1 watch

1. So I'm confused on a question on June 2014 OCR M1 and the mark scheme doesn't help me. It says
Particles P and Q move towards each other with speeds 4m/s and 2m/s along a smooth surface. P has mass 0.2 and Q 0.3. They collide. Show that Q changes direction.

So I can do conservation of linear momentum but I can't figure out how you can know what direction a velocity is going without knowing its actual value. The mark scheme says the marks are as follows:

Calculation for both “before” Momentum (magnitudes)
Compares both terms without arithmetic error
Shows direction of after total momentum conflicts with the before velocity/momentum of Q

I don't understand how you can infer direction with two unknown 'after' velocities.

I have the equation
0.2 = 0.2V1 + 0.3V2

Can anyone explain it better than the mark scheme?
2. Sorry you've not had any responses about this. Are you sure you've posted in the right place? Here's a link to our subject forum which should help get you more responses if you post there.

You can also find the Exam Thread list for A-levels here and GCSE here.

Just quoting in Puddles the Monkey so she can move the thread if needed
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(Original post by Puddles the Monkey)
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Updated: June 18, 2016
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