I'm going wrong somewhere but don't know where. Can someone help? Thanks in advance.

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Q: Two particles P and Q of masses $\displaystyle 3kg$ and $\displaystyle 6kg$ respectively are attached to the ends of a light inextensible string. The string is released from rest with both masses a distance of 2m above a horizontal floor. Find how long it takes for the particle Q to hit the floor.

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My attempt:

$\displaystyle (P): T - 3g = 3a$ ------------$\displaystyle (1)$

$\displaystyle (Q): 6g - T = 6a$ ------------$\displaystyle (2)$

$\displaystyle (1) + (2) \implies a=\frac{1}{3} ms^{-2}$

$\displaystyle \therefore \text{Using }s=ut + \frac{1}{2} a t^2.$ $\displaystyle \text{Where }s=2, u=0, a=\frac{1}{3}$

$\displaystyle t= \sqrt \frac{2s}{a}$

$\displaystyle t=3.46s$

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But...The real answer is $\displaystyle t=1.11s$ so where have I gone wrong? :confused: