Two trolleys

Diagram below shows two trolleys, M and N of the same mass before and after collision.

Rajah di bawah menunjukkan dua troli M dan N yang berjisim sama sebelum dan selepas
perlanggaran.



Which is true about u and v?
Manakah benar mengenai u dan v? 
 
A    v = u
B    v > u
C   u = 2v
D   v = 2u
 
 
 
 
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Answer
 
C